Exhibit 99.1

NEWS RELEASE

Contact:

Alliance HealthCare Services

Howard Aihara

Executive Vice President

Chief Financial Officer

(949) 242-5300

ALLIANCE HEALTHCARE SERVICES REPORTS RESULTS

FOR THE FIRST QUARTER ENDED MARCH 31, 2011

AND REAFFIRMS FULL YEAR 2011 GUIDANCE

NEWPORT BEACH, CA—April 28, 2011–Alliance HealthCare Services, Inc. (NYSE:AIQ) (the “Company” or “Alliance”), a leading national provider of outpatient diagnostic imaging and radiation therapy services, announced results for the first quarter ended March 31, 2011.

First Quarter 2011 Financial Results

Revenue for the first quarter of 2011 was $118.4 million compared to $118.7 million in the first quarter of 2010, a decrease of 0.2%. On a sequential quarter basis, revenue increased 0.6% to $118.4 million in the first quarter of 2011 compared to $117.7 million in the fourth quarter of 2010.

Alliance’s Adjusted EBITDA (as defined below) was $36.6 million in the first quarter of 2011 compared to $40.2 million in the first quarter 2010, a decrease of 9.0%. On a sequential quarter basis, Adjusted EBITDA increased 4.6% to $36.6 million in the first quarter of 2011 compared to $35.0 million in the fourth quarter of 2010.

Alliance’s net loss, computed in accordance with generally accepted accounting principles (“GAAP”), totaled ($2.4) million in the first quarter of 2011 and ($2.2) million in the first quarter of 2010.

Net loss per share on a diluted basis, computed in accordance with generally GAAP, was ($0.05) per share in the first quarter of 2011 and ($0.04) per share in the first quarter of 2010. In the first quarter of 2011, net loss per share on a diluted basis was impacted by ($0.02) in the aggregate due to fair value adjustments related to interest rate swaps, severance and related costs, mergers and acquisitions transaction costs and a lower GAAP income tax rate than our historical income tax rate. Alliance’s historical income tax rate has been approximately 42%, rather than the GAAP income tax benefit rate of 35.9% in the first quarter of 2011.

Cash flows provided by operating activities were $19.5 million in the first quarter of 2011 compared to $30.7 million in the first quarter of 2010. Capital expenditures in the first quarter of 2011 were $9.9 million compared to $20.2 million in the first quarter of 2010. Alliance opened five new fixed-site imaging centers in the first quarter of 2011.

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Alliance HealthCare Services

Press Release

April 28, 2011

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Alliance’s net debt, defined as total long-term debt (including current maturities) less cash and cash equivalents, decreased $6.9 million to $549.2 million at March 31, 2011 from $556.1 million at December 31, 2010. Cash and cash equivalents were $101.9 million at March 31, 2011 and $97.2 million at December 31, 2010. The Company’s net debt, as defined above, divided by the last twelve months Adjusted EBITDA (pro forma for acquisitions during the last twelve month period ended March 31, 2011), was 3.5x for the twelve month period ended March 31, 2011.

The Company’s total long-term debt (including current maturities) decreased to $651.1 million at March 31, 2011 from $653.3 million at December 31, 2010. The Company’s total long-term debt (including current maturities) divided by last twelve months Adjusted EBITDA (pro forma for acquisitions during the last twelve month period ended March 31, 2011) was 4.2x for the twelve month period ended March 31, 2011.

Paul S. Viviano, Chairman of the Board and Chief Executive Officer, stated, “Alliance continues to perform consistent with our full year 2011 guidance. We are pleased with the progress of first quarter Adjusted EBITDA relative to the fourth quarter of 2010. We are very pleased regarding the two recently announced acquisitions: US Radiosurgery and 24/7 Radiology. These investments reflect our commitment to expanding our presence in the growth oriented clinical service lines of radiation oncology and professional radiology services. The integration of these two organizations continues to progress well and in accordance with our plan. Alliance continues to focus on increasingly becoming the hospital outsource partner of choice through the development of new fixed site imaging centers, adding new customers for MRI, PET/CT and professional radiology services and developing new de novo radiation oncology centers.”

Full Year 2011 Guidance

Alliance reaffirms its full year 2011 guidance ranges:

First Quarter 2011 Earnings Conference Call

Investors and all others are invited to listen to a conference call discussing first quarter 2011 results. The conference call is scheduled for Friday, April 29, 2011 at 8:30 a.m. Eastern Time. The call will be broadcast live on the Internet and can be accessed by visiting the Company’s website at www.alliancehealthcareservices-us.com. Click on Audio Presentations in the Investors section of the website to access the link.

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Alliance HealthCare Services

Press Release

April 28, 2011

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The conference call can be accessed at (888) 694-4676 (United States) or (973) 582-2737 (International). Interested parties should call at least 5 minutes prior to the call to register. A telephone replay will be available until July 29, 2011. The telephone replay can be accessed by calling (800) 642-1687 (United States) or (706) 645-9291 (International). The conference call identification number is 61776694.

Definition of Adjusted EBITDA

Adjusted EBITDA, as defined by the Company’s management, represents net income (loss) before: interest expense, net of interest income; income taxes; depreciation expense; amortization expense; net income (loss) attributable to noncontrolling interests; non-cash share-based compensation; severance and related costs; loss on extinguishment of debt; fees and expenses related to acquisitions, non-cash impairment charges, and other non-cash charges included in other (income) expense, net, which includes non-cash losses on sales of equipment. The components used to reconcile net income (loss) to Adjusted EBITDA are consistent with our historical presentation of Adjusted EBITDA. Adjusted EBITDA is not a measure of financial performance under generally accepted accounting principles in the United States, or “GAAP.” For a more detailed discussion of Adjusted EBITDA and reconciliation to net income (loss), see the section entitled “Adjusted EBITDA” included in the tables following this release.

About Alliance HealthCare Services

Alliance HealthCare Services is a leading national provider of advanced outpatient diagnostic imaging and radiation therapy services based upon annual revenue and number of systems deployed. Alliance focuses on MRI, PET/CT and CT through its Imaging division and radiation therapy through its Oncology division. With more than 2,300 team members committed to providing exceptional patient care and exceeding customer expectations, Alliance provides quality clinical services for over 1,000 hospitals and other healthcare partners in 46 states. Alliance operates 559 diagnostic imaging and radiation therapy systems. The Company is the nation’s largest provider of advanced diagnostic mobile imaging services and one of the leading operators of fixed-site imaging centers, with 136 locations across the country. Alliance also operates 35 radiation therapy centers, providing state-of-the-art treatment and care for cancer patients.

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Alliance HealthCare Services

Press Release

April 28, 2011

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Forward-Looking Statements

This press release contains forward-looking statements relating to future events, including statements related to investment, development and acquisition activity, the implementation of strategic initiatives, the integration of acquired businesses into the Company, the opening of new imaging and radiation oncology centers, and the Company’s full year 2011 guidance. In this context, forward-looking statements often address the Company’s expected future business and financial results and often contain words such as “expects,” “anticipates,” “intends,” “plans,” “believes,” “seeks” or “will.” Forward-looking statements by their nature address matters that are uncertain and subject to risks. Such uncertainties and risks include: changes in the preliminary financial results and estimates due to the restatement or review of the Company’s financial statements; the nature, timing and amount of any restatement or other adjustments; the Company’s ability to make timely filings of its required periodic reports under the Securities Exchange Act of 1934; issues relating to the Company’s ability to maintain effective internal control over financial reporting and disclosure controls and procedures; the Company’s high degree of leverage and its ability to service its debt; factors affecting the Company’s leverage, including interest rates; the risk that the counterparties to the Company’s interest rate swap agreements fail to satisfy their obligations under these agreements; the Company’s ability to obtain financing; the effect of operating and financial restrictions in the Company’s debt instruments; the accuracy of the Company’s estimates regarding its capital requirements; the effect of intense levels of competition in the Company’s industry; changes in the methods of third party reimbursements for diagnostic imaging and radiation oncology services; fluctuations or unpredictability of the Company’s revenues, including as a result of seasonality; changes in the healthcare regulatory environment; the Company’s ability to keep pace with technological developments within its industry; the growth in the market for MRI and other services; the disruptive effect of hurricanes and other natural disasters; adverse changes in general domestic and worldwide economic conditions and instability and disruption of credit markets; difficulties the Company may face in connection with recent, pending or future acquisitions, including unexpected costs or liabilities resulting from the acquisitions, diversion of management’s attention from the operation of the Company’s business, and risks associated with integration of the acquisitions; and other risks and uncertainties identified in the Risk Factors section of the Company’s Form 10-K for the year ended December 31, 2010, filed with the Securities and Exchange Commission (the “SEC”), as may be modified or supplemented by our subsequent filings with the SEC. These uncertainties may cause actual future results or outcomes to differ materially from those expressed in the Company’s forward-looking statements. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. The Company does not undertake to update its forward-looking statements except as required under the federal securities laws.

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ALLIANCE HEALTHCARE SERVICES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

AND COMPREHENSIVE INCOME (LOSS)

(Unaudited)

(in thousands, except per share amounts)

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ALLIANCE HEALTHCARE SERVICES, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(Unaudited)

(in thousands)

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ALLIANCE HEALTHCARE SERVICES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

(in thousands)

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ALLIANCE HEALTHCARE SERVICES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (continued)

(Unaudited)

(in thousands)

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ALLIANCE HEALTHCARE SERVICES, INC.

ADJUSTED EBITDA

(in thousands)

Adjusted EBITDA, as defined by the Company’s management, represents net income (loss) before: interest expense, net of interest income; income taxes; depreciation expense; amortization expense; net income (loss) attributable to noncontrolling interests; non-cash share-based compensation; severance and related costs; loss on extinguishment of debt; fees and expenses related to acquisitions, non-cash impairment charges, and other non-cash charges included in other (income) expense, net, which includes non-cash losses on sales of equipment. The components used to reconcile net income (loss) to Adjusted EBITDA are consistent with our historical presentation of Adjusted EBITDA. Adjusted EBITDA is not a measure of financial performance under generally accepted accounting principles in the United States, or “GAAP.”

Management uses Adjusted EBITDA, and believes it is a useful measure for investors, for a variety of reasons. Management regularly communicates its Adjusted EBITDA results and management’s interpretation of such results to its board of directors. Management also compares the Company’s Adjusted EBITDA performance against internal targets as a key factor in determining cash incentive compensation for executives and other employees, largely because management feels that this measure is indicative of how our diagnostic imaging and radiation oncology business is performing and is being managed. Management believes that Adjusted EBITDA is a particularly useful comparative measure within the Company’s industry. The diagnostic imaging and radiation oncology industry continues to experience significant consolidation. These activities have led to significant charges to earnings, such as those resulting from acquisition costs, and to significant variations among companies with respect to capital structures and cost of capital (which affect interest expense) and differences in taxation and book depreciation of facilities and equipment (which affect relative depreciation expense), including significant differences in the depreciable lives of similar assets among various companies. In addition, management believes that because of the variety of equity awards used by companies, the varying methodologies for determining non-cash share-based compensation expense among companies and from period to period, and the subjective assumptions involved in that determination, excluding non-cash share-based compensation from Adjusted EBITDA enhances company-to-company comparisons over multiple fiscal periods and enhances the Company’s ability to analyze the performance of its diagnostic imaging and radiation oncology business.

Adjusted EBITDA may not be directly comparable to similarly titled measures reported by other companies. In addition, Adjusted EBITDA has other limitations as an analytical financial measure. These limitations include the fact that Adjusted EBITDA is calculated before recurring cash charges including interest expense, income taxes and severance costs, and is not adjusted for capital expenditures, the replacement cost of assets or other recurring cash requirements of the Company’s business. Adjusted EBITDA also does not reflect any cost for equity awards to employees. In the future, the Company expects that it may incur expenses similar to the excluded items discussed above. Accordingly, the exclusion of these and other similar items in the Company’s non-GAAP presentation should not be interpreted as implying that these items are non-recurring, infrequent or unusual. Management compensates for the limitations of using Adjusted EBITDA as an analytical measure by relying on the Company’s GAAP results to evaluate its operating performance and by considering independently the economic effects of the items that are or are not reflected in Adjusted EBITDA. Management also compensates for these limitations by providing GAAP-based disclosures concerning the excluded items in the Company’s financial disclosures. As a result of these limitations, however, Adjusted EBITDA should not be considered as an alternative to net income (loss), as calculated in accordance with GAAP, or as an alternative to any other GAAP measure of operating performance.

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The calculation of Adjusted EBITDA is shown below:

The reconciliation from net loss to Adjusted EBITDA for the 2011 guidance range is shown below (in millions):

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ALLIANCE HEALTHCARE SERVICES, INC.

SELECTED STATISTICAL INFORMATION

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ALLIANCE HEALTHCARE SERVICES, INC.

SELECTED STATISTICAL INFORMATION

IMAGING DIVISION REVENUE GAP

(in millions)

The Company utilizes the imaging division revenue gap as a statistical measure of its client losses and new client contracts. The imaging division revenue gap is calculated by measuring the difference between (a) the quarterly imaging division revenue run rate lost as a result of clients choosing to terminate contracts with the Company, excluding clients for which Alliance provides professional radiology services, interim service and clients that the Company elects to terminate, and (b) projected quarterly new imaging division revenue from new client contracts, excluding professional radiology services, commencing service in the quarter.

The imaging division revenue gap for the last eight calendar quarters and the last twelve month period ended March 31, 2011 is as follows:

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