Exhibit 99.1

Cogent Communications Reports First Quarter 2018 Results
and Increases Regular Quarterly Dividend on Common Stock

Financial and Business Highlights

·                  Cogent approves a 4.0% increase of $0.02 per share to its regular quarterly dividend to $0.52

·                  Service revenue increased by 2.8% from Q4 2017 to Q1 2018 to $128.7 million and increased from Q1 2017 to Q1 2018 by 9.8%

·                  On- net revenue increased by 3.4% from Q4 2017 to Q1 2018 to $92.4 million and increased from Q1 2017 to Q1 2018 by 10.5%

·                  Off- net revenue increased by 1.4% from Q4 2017 to Q1 2018 to $36.1 million and increased from Q1 2017 to Q1 2018 by 8.3%

·                  Cash flow from operations for Q1 2018 increased by 28.3% from Q1 2017 to $30.2 million

·                  EBITDA for Q1 2018 increased by 16.9% from Q1 2017 to $44.1 million

·                  EBITDA margin for Q1 2018 increased by 210 basis points to 34.3% from Q1 2017

[WASHINGTON, D.C. May 3, 2018] Cogent Communications Holdings, Inc. (NASDAQ: CCOI) today announced service revenue of $128.7 million for the three months ended March 31, 2018, an increase of 9.8% from the three months ended March 31, 2017 and an increase of 2.8% from the three months ended December 31, 2017. Foreign exchange positively impacted service revenue growth from the three months ended December 31, 2017 to the three months ended March 31, 2018 by $1.0 million and positively impacted service revenue growth from the three months ended March 31, 2017 to the three months ended March 31, 2018 by $3.3 million.  On a constant currency basis, service revenue grew by 2.0% from the three months ended December 31, 2017 to the three months ended March 31, 2018 and grew by 7.0% from the three months ended March 31, 2017 to the three months ended March 31, 2018.

On-net service is provided to customers located in buildings that are physically connected to Cogent’s network by Cogent facilities. On-net revenue was $92.4 million for the three months

ended March 31, 2018; an increase of 3.4% from the three months ended December 31, 2017 and an increase of 10.5% over the three months ended March 31, 2017.

Off-net customers are located in buildings directly connected to Cogent’s network using other carriers’ facilities and services to provide the last mile portion of the link from the customers’ premises to Cogent’s network. Off-net revenue was $36.1 million for the three months ended March 31, 2018; an increase of 1.4% over the three months ended December 31, 2017 and an increase of 8.3% over the three months ended March 31, 2017.

GAAP gross profit is defined as total service revenue less network operations expense, depreciation and amortization and equity based compensation included in network operations expense.  GAAP gross margin is defined as GAAP gross profit divided by total service revenue. GAAP gross profit increased by 12.6% from the three months ended March 31, 2017 to $54.0 million for the three months ended March 31, 2018 and increased by 4.0% from the three months ended December 31, 2017. GAAP gross margin was 42.0% for the three months ended March 31, 2018, 41.0% for the three months ended March 31, 2017 and 41.5% for the three months ended December 31, 2017.  Excise taxes, including Universal Service Fund fees, recorded on a gross basis and included in service revenue and cost of network operations expense were $3.2 million for the three months ended March 31, 2018, $2.9 million for the three months ended December 31, 2017 and $2.6 million for the three months ended March 31, 2017.

Non-GAAP gross profit represents service revenue less network operations expense, excluding equity-based compensation and amounts shown separately (depreciation and amortization expense). Non-GAAP gross margin is defined as non-GAAP gross profit divided by total service revenue.  Non-GAAP gross profit increased by 11.1% from the three months ended March 31, 2017 to $74.0 million for the three months ended March 31, 2018 and increased by 3.6% from the three months ended December 31, 2017. Non-GAAP gross profit margin was 57.5% for the three months ended March 31, 2018, 56.9% for the three months ended March 31, 2017 and 57.1% for the three months ended December 31, 2017.

Cash flow from operating activities increased by 28.3% from the three months ended March 31, 2017 to $30.2 million for the three months ended March 31, 2018 and decreased by 3.8% from the three months ended December 31, 2017.

Earnings before interest, taxes, depreciation and amortization (EBITDA) increased by 16.9% from the three months ended March 31, 2017 to $44.1 million for the three months ended March 31, 2018 and increased by 2.0% from the three months ended December 31, 2017. EBITDA margin was 34.3% for the three months ended March 31, 2018, 32.2% for the three months ended March 31, 2017 and 34.5% for the three months ended December 31, 2017.

EBITDA, as adjusted, increased by 10.9% from the three months ended March 31, 2017 to $44.2 million for the three months ended March 31, 2018 and increased by 1.5% from the three months ended December 31, 2017. EBITDA, as adjusted, margin was 34.3% for the three months ended March 31, 2018, 34.0% for the three months ended March 31, 2017 and 34.8% for the three months ended December 31, 2017.

Basic and diluted net income (loss) per share was $0.15 for the three months ended March 31, 2018, $0.09 for the three months ended March 31, 2017 and $(0.14) for the three months ended December 31, 2017.

Total customer connections increased by 15.1% from March 31, 2017 to 73,914 as of March 31, 2018 and increased by 3.2% from December 31, 2017. On-net customer connections increased by 15.6% from March 31, 2017 to 63,366 as of March 31, 2018 and increased by 3.3% from December 31, 2017. Off-net customer connections increased by 13.1% from March 31, 2017 to 10,241 as of March 31, 2018 and increased by 2.9% from December 31, 2017.

The number of on-net buildings increased by 135 on-net buildings from March 31, 2017 to 2,541 on-net buildings as of March 31, 2018 and increased by 35 on-net buildings from December 31, 2017.

Quarterly Dividend Increase Approved

On May 2, 2018, Cogent’s board approved a regular quarterly dividend of $0.52 per common share payable on June 1, 2018 to shareholders of record on May 17, 2018. This second quarter 2018 regular dividend represents a 4.0% increase of $0.02 per share from the first quarter 2018 regular dividend of $0.50 per share.

The payment of any future dividends and any other returns of capital will be at the discretion of Cogent’s board of directors and may be reduced, eliminated or increased and will be dependent

upon Cogent’s financial position, results of operations, available cash, cash flow, capital requirements, limitations under Cogent’s debt indenture agreements and other factors deemed relevant by Cogent’s board of directors.

Conference Call and Website Information

Cogent will host a conference call with financial analysts at 8:30 a.m. (ET) on May 3, 2018 to discuss Cogent’s operating results for the first quarter of 2018 and to discuss Cogent’s expectations for full year 2018. Investors and other interested parties may access a live audio webcast of the earnings call in the “Events” section of Cogent’s website at www.cogentco.com/events. A replay of the webcast, together with the press release, will be available on the website following the earnings call.

About Cogent Communications

Cogent Communications (NASDAQ: CCOI) is a multinational, Tier 1 facilities-based ISP.  Cogent specializes in providing businesses with high speed Internet access, Ethernet transport, and colocation services. Cogent’s facilities-based, all-optical IP network backbone provides services in over 195 markets globally.

Cogent Communications is headquartered at 2450 N Street, NW, Washington, D.C. 20037. For more information, visit www.cogentco.com. Cogent Communications can be reached in the United States at (202) 295-4200 or via email at info@cogentco.com.

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COGENT COMMUNICATIONS HOLDINGS, INC., AND SUBSIDIARIES

Summary of Financial and Operational Results

(1)         Consists of legacy services of companies whose assets or businesses were acquired by Cogent, primarily including voice services (only provided in Toronto, Canada).

(2)         Network operations expense excludes equity-based compensation expense of $111, $141, $179, $173 and $189 in the three month periods ended March 31, 2017 through March 31, 2018, respectively.  Network operations expense includes excise taxes, including Universal Service Fund fees of $2,604, $2,672, $2,691, $2,943 and $3,157 in the three month periods ended March 31, 2017 through March 31, 2018, respectively.

(3)         GAAP gross profit is defined as total service revenue less network operations expense, depreciation and amortization and equity based compensation included in network operations expense.  GAAP gross margin is defined as GAAP gross profit divided by total service revenue.

(4)         Non-GAAP gross profit represents service revenue less network operations expense, excluding equity-based compensation and amounts shown separately (depreciation expense). Non-GAAP gross margin is defined as non-GAAP gross profit divided by total service revenue.  Management believes that Non-GAAP gross profit and Non-GAAP gross profit margin are relevant metrics to provide investors, as they are metrics that management uses to measure the margin available to the company after network service costs, in essence a measure of the efficiency of the Company’s network.

(5)         Excludes equity-based compensation expense of $2,536, $3,084, $3,555, $3,511 and $3,595 in the three month periods ended March 31, 2017 through March 31, 2018, respectively.

(6)         See schedule of non-GAAP metrics below for definitions and reconciliations to GAAP measures below.

Schedules of Non-GAAP Measures

EBITDA and EBITDA, as adjusted

EBITDA represents net cash flows from operating activities plus changes in operating assets and liabilities, cash interest expense and cash income tax expense.  Management believes the most directly comparable measure to EBITDA calculated in accordance with generally accepted accounting principles in the United States, or GAAP, is cash flows provided by operating activities. The Company also believes that EBITDA is a measure frequently used by securities analysts, investors, and other interested parties in their evaluation of issuers.  EBITDA, as adjusted, represents EBITDA plus net gains (losses) on asset related transactions.

The Company believes that EBITDA, and EBITDA, as adjusted, are useful measures of its ability to service debt, fund capital expenditures and expand its business.  EBITDA, and EBITDA, as adjusted are an integral part of the internal reporting and planning system used by management as a supplement to GAAP financial information. EBITDA, and EBITDA, as adjusted are not recognized terms under GAAP and accordingly, should not be viewed in isolation or as a substitute for the analysis of results as reported under GAAP, but rather as a supplemental measure to GAAP. For example, these metrics are not intended to reflect the Company’s free cash flow, as it does not consider certain current or future cash requirements, such as capital expenditures, contractual commitments, and changes in working capital needs, interest expenses and debt service requirements. The Company’s calculations of these metrics may also differ from the calculations performed by its competitors and other companies and as such, its utility as a comparative measure is limited.

EBITDA, and EBITDA, as adjusted, are reconciled to cash flows provided by operating activities in the table below.

Constant currency revenue is reconciled to service revenue as reported in the tables below.

Constant currency impact on revenue changes — sequential periods

(1)         Service revenue, as adjusted for currency impact, is determined by translating the service revenue for the current period at the average foreign currency exchange rates for the prior sequential period. The Company believes that disclosing quarterly sequential revenue growth without the impact of foreign currencies on service revenue is a useful measure of sequential revenue growth. Service revenue, as adjusted for currency impact, is an integral part of the internal reporting and planning system used by management as a supplement to GAAP financial information.

Constant currency impact on revenue changes — prior year periods

(2)         Service revenue, as adjusted for currency impact, is determined by translating the service revenue for the current period at the average foreign currency exchange rates for the comparable prior year period. The Company believes that disclosing year over year revenue growth without the impact of foreign currencies on service revenue is a useful measure of revenue growth. Service revenue, as adjusted for currency impact, is an integral part of the internal reporting and planning system used by management as a supplement to GAAP financial information.

Non-GAAP gross profit and Non-GAAP gross margin

Non-GAAP gross profit and Non-GAAP gross margin are reconciled to GAAP gross profit and GAAP gross margin in the table below.

(1)         GAAP gross profit is defined as total service revenue less network operations expense, depreciation and amortization and equity based compensation included in network operations expense.  GAAP gross margin is defined as GAAP gross profit divided by total service revenue.

(2)         Non-GAAP gross profit represents service revenue less network operations expense, excluding equity-based compensation and amounts shown separately (depreciation and amortization expense). Non-GAAP gross margin is defined as non-GAAP gross profit divided by total service revenue.  Management believes that non-GAAP gross profit and non-GAAP gross margin are relevant metrics

to provide to investors, as they are metrics that management uses to measure the margin and amount available to the Company after network service costs, in essence these are measures of the efficiency of the Company’s network.

Gross and Net Leverage Ratios

Gross leverage ratio is defined as total debt divided by the trailing last 12 months EBITDA, as adjusted.  Net leverage ratio is defined as total net debt (total debt minus cash and cash equivalents) divided by the trailing last 12 months EBITDA, as adjusted.  Cogent’s gross leverage ratio was 4.44 at December 31, 2017 and 4.33 at March 31, 2018 and Cogent’s net leverage ratio was 2.94 at December 31, 2017 and 2.94 at March 31, 2018 and as shown below.

Cogent’s SEC filings are available online via the Investor Relations section of www.cogentco.com or on the Securities and Exchange Commission’s website at www.sec.gov.

COGENT COMMUNICATIONS HOLDINGS, INC., AND SUBSIDIARIES

CONDENSED CONSOLIDATED BALANCE SHEETS

AS OF MARCH 31, 2018 AND DECEMBER 31, 2017

(IN THOUSANDS, EXCEPT SHARE DATA)

COGENT COMMUNICATIONS HOLDINGS, INC., AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

FOR THE THREE MONTHS ENDED MARCH 31, 2018 AND MARCH 31, 2017

(IN THOUSANDS, EXCEPT SHARE AND PER SHARE AMOUNTS)

COGENT COMMUNICATIONS HOLDINGS, INC., AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

FOR THE THREE MONTHS ENDED MARCH 31, 2018 AND MARCH 31, 2017

(IN THOUSANDS)

Except for historical information and discussion contained herein, statements contained in this release constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995.  Such statements include, but are not limited to statements identified by words such as “believes,” “expects,” “anticipates,” “estimates,” “intends,” “plans,” “targets,” “projects” and similar expressions.  The statements in this release are based upon the current beliefs and expectations of Cogent’s management and are subject to significant risks and uncertainties.  Actual results may differ from those set forth in the forward-looking statements.  Numerous factors could cause or contribute to such differences, including future economic instability in the global economy or a contraction of the capital markets which could affect spending on Internet services and our ability to engage in financing activities; the impact of changing foreign exchange rates (in particular the Euro to USD and Canadian dollar to USD exchange rates) on the translation of our non-USD denominated revenues, expenses, assets and liabilities; legal and operational difficulties in new markets; the imposition of a requirement that we contribute to the US Universal Service Fund on the basis of our Internet revenue; changes in government policy and/or regulation, including net neutrality rules  by the United States Federal Communications Commission and in the area of data protection; increasing competition leading to lower prices for our services; our ability to attract new customers and to increase and maintain the volume of traffic on our network; the ability to maintain our Internet peering arrangements on favorable terms; our reliance on an equipment vendor, Cisco Systems Inc., and the potential for hardware or software problems associated with such equipment; the dependence of our network on the quality and dependability of third-party fiber providers; our ability to retain certain customers that comprise a significant portion of our revenue

base; the management of network failures and/or disruptions; and outcomes in litigation as well as other risks discussed from time to time in our filings with the Securities and Exchange Commission, including, without limitation, our report on Form 10-Q  for the quarter ended March 31, 2018 to be filed with the Securities and Exchange Commission. Cogent undertakes no duty to update any forward-looking statement or any information contained in this press release or in other public disclosures at any time.

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