It is widely supposed that it is important to ensure that patients undergoing medical procedures hope that their treatments will be successful. But why is hope so important, if indeed it is? After examining the answers currently on offer in the literature, we identify a hitherto unrecognized reason for supposing that it is important that patients possess hope for a successful treatment, which draws on prospect theory, Kahneman and Tversky’s hugely influential descriptive theory about decision-making in situations of risk and (...) uncertainty. We also consider some concerns about patient consent and the potential manipulation of patients that are raised by our account. (shrink)