Do inpatient hospitals providing a select number of services produce improved outcomes through specialization, or do the apparent benefits of these specialty hospitals result from a selection of healthier patients? In addressing this question, this article focuses on whether increased cardiac specialization of a hospital's services is associated with improved outcomes for patients undergoing coronary artery bypass graft (CABG) surgery. The authors studied Medicare beneficiaries undergoing CABG from 2001 to 2003 and found that the quality of care that they received at cardiac specialty hospitals was similar to care provided at general hospitals. Mortality rates, post-discharge emergency room visits and hospital readmission rates were not significantly related to the choice of a specialty hospital over a generalist competitor. Patients with a greater degree of coexistent conditions or diseases that are not cardiovascular in nature experienced poorer 30-day mortality rates after discharge from cardiac specialty hospitals, however. This suggests that hospitals with cardiac specialization may not be the best choice for patients who may require greater coordination and management of their care.