Decision-related regret is a negative emotion associated with thinking about a past or future choice. The thinking component generally takes the form of a wish that things were otherwise and involves a comparison of what actually did or will take place with some better alternative--a "counterfactual thought." For predecisional (anticipated) regret, the thinking involves a mental simulation of the outcomes that might result from different choice options. Prior research has focused on regret associated with decision outcomes, addressing especially (a) the comparison outcome selected and (b) whether the outcome resulted from action or inaction. More recent research examines regret associated with the choice itself and with the preceding decision process. Interest here has focused on the justifiability of the choice made or the process used. In this article, the authors review current regret research and propose directions for extending it to cancer-related decisions.