BACKGROUND: In October 2012, The Centers for Medicare and Medicaid Services (CMS) began publicly reporting American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) surgical outcomes on its public reporting website, Hospital Compare. Participation in this CMS-NSQIP initiative is voluntary. Our objective was to compare CMS-NSQIP participating hospitals with ACS NSQIP hospitals that elected not to participate. STUDY DESIGN: Hospital Compare and American Hospital Association Annual Survey data were merged to compare CMS-NSQIP participants with nonparticipants. Regression models were developed to assess predictors of participation and to assess if hospitals differed on 32 process, 10 patient experience (Hospital Consumer Assessment of HealthCare Providers and Systems [HCAHPS]), and 16 outcomes (Hospital Compare and Agency for Healthcare Research Quality) measures. Additionally, performance on 2 waves of publicly reported ACS NSQIP surgical outcomes measures was compared. RESULTS: Of the 452 ACS NSQIP hospitals, 80 (18%) participated in CMS-NSQIP public reporting. Participating hospitals had more beds, admissions, operations, and were more often accredited (Commission on Cancer and the Council of Teaching Hospitals [COTH] [p < 0.05]). Only COTH membership remained significant in adjusted analyses (odds ratio 2.45, 95% CI 1.12 to 5.35). Hospital performance on process, HCAHPS, and outcomes measures were not associated with CMS-NSQIP participation for 54 of 58 measures examined. Hospitals with "better-than-average" performance were more likely to publicly report the Elderly Surgery measure (p < 0.05). In wave 2, an increased proportion of new participants reported "worse-than-average" outcomes. CONCLUSIONS: There were few measurable differences between CMS-NSQIP participating and nonparticipating hospitals. The decision to voluntarily publicly report may be related to the hospital's culture of quality improvement and transparency.