Prior research has shown that people mispredict their own behavior and preferences across affective states. When people are in an affectively "cold" state, they fail to fully appreciate how "hot" states will affect their own preferences and behavior. When in hot states, they underestimate the influence of those states and, as a result, overestimate the stability of their current preferences. The same biases apply interpersonally; for example, people who are not affectively aroused underappreciate the impact of hot states on other people's behavior. After reviewing research documenting such intrapersonal and interpersonal hot-cold empathy gaps, this article examines their consequences for medical, and specifically cancer-related, decision making, showing, for example, that hot-cold empathy gaps can lead healthy persons to expose themselves excessively to health risks and can cause health care providers to undertreat patients for pain.