People tend to be comparatively optimistic (i.e., believe that negative outcomes are less likely for themselves than for typical others) regarding their susceptibility to negative health outcomes. The present study investigates the extent to which perceptions of the severity of these health outcomes show similar comparative optimism. A student sample (study 1; N = 200) and a healthy non-student adult sample (study 2; N = 257) completed self-report measures of susceptibility, severity, worry, control and experience in relation to negative health outcomes. Participants in both studies demonstrated significant levels of comparative optimism for both perceived likelihood and severity of health outcomes. Comparative optimism concerning severity was very strongly associated (r = 0.85 to 0.89) with comparative optimism concerning susceptibility. In addition to being comparatively optimistic over their chances of experiencing negative health outcomes, people are also comparatively optimistic regarding how severe the health outcomes will be.