The optimistic bias is defined as judging one's own risk as less than the risk of others. Researchers have identified numerous personal and situational factors that moderate the extent to which people display the bias. It is unclear, however, whether these moderators affect the bias by influencing people's personal risk estimates or their risk estimates for a target. A review of moderators of the optimistic bias reveals evidence for both influences. Moderators associated with negative affect (negative mood, dysphoria, trait and state anxiety, event severity, and proximity of feedback) and control related moderators (perceived control and prior experience) appear primarily to affect personal risk estimates. Positive mood affects target risk estimates. Finally, moderators that surround the comparison process appear to have different effects. Specifically, the type of comparison target appears to affect target risk estimates, whereas attention to personal risk-related behaviors affects personal risk estimates.