Comparative effectiveness research (CER) can provide valuable information for patients, providers and payers. These stakeholders differ in their incentives to invest in CER. To maximize benefits from public investments in CER, it is important to understand the value of CER from the perspectives of these stakeholders and how that affects their incentives to invest in CER. This article provides a conceptual framework for valuing CER, and illustrates the potential benefits of such studies from a number of perspectives using several case studies. We examine cases in which CER provides value by identifying when one treatment is consistently better than others, when different treatments are preferred for different subgroups, and when differences are small enough that decisions can be made based on price. We illustrate these findings using value-of-information techniques to assess the value of research, and by examining changes in pharmaceutical prices following publication of a comparative effectiveness study. Our results suggest that CER may have high societal value but limited private return to providers or payers. This suggests the importance of public efforts to promote the production of CER. We also conclude that value-of-information tools may help inform policy decisions about how much public funds to invest in CER and how to prioritize the use of available public funds for CER, in particular targeting public CER spending to areas where private incentives are low relative to social benefits.