We review explanations offered by researchers for optimism in comparative risk judgments – the belief that one is at lower risk than other people for negative events. Our review organizes the explanations into four categories. The categories reflect a) the desired end-states of comparative judgments, b) the cognitive processes that guide judgments, c) the information people have or use in making judgments, and d) the underlying affect. For each explanation we review relevant studies. We conclude by discussing whether comparative optimism reflects a distortion in personal risk judgments or judgments of the average person’s risk, by addressing the interplay of the various accounts of comparative optimism, and by discussing directions for future research.