Little is known about which hospitals participate in voluntary public reporting of quality processes and what influences their performance, particularly in cancer care. We hypothesize that patient volume is positively associated with both reporting and performance. In 2014, when Pennsylvania became the first and only state to have public reporting for cancer care, it became possible to test these hypotheses, which we did in cross-sectional study of the 72 Pennsylvania hospitals accredited by the Commission on Cancer. Hospitals that publicly reported their performance (57 of 72) had higher patient volumes than hospitals that did not release performance. Among reporting hospitals, no association was found between patient volume and performance on process of care metrics. These findings suggest the importance of attending to volume effects in public reporting of cancer care and recognizing that volume is not a predictor of performance for reporting hospitals, which indicates the need for research to identify other factors that differentiate performance within and across reporting and nonreporting hospitals.