Healthy people generally underestimate the self-reported well-being of people with disabilities and serious illnesses. The cause of this discrepancy is in dispute, and the present study provides evidence for 2 causes. First, healthy people fail to anticipate hedonic adaptation to poor health. Using an ecological momentary assessment measure of mood, the authors failed to find evidence that hemodialysis patients are less happy than healthy nonpatients are, suggesting that they have largely, if not completely, adapted to their condition. In a forecasting task, healthy people failed to anticipate this adaptation. Second, although controls understated their own mood in both an estimation task and a recall task, patients were quite accurate in both tasks. This relative negativity in controls' estimates of their own moods could also contribute to their underestimation of the moods and overall well-being of patients.