Using an experimental manipulation embedded in a national survey, this study investigated the effect on smokers' risk judgments of receiving accurate information about the cigarette consumption of the average smoker. It was hypothesized that this information would reduce smokers' estimates of the risk of lung cancer faced by the average smoker (‘other's risk’) and hence influence their comparative risk judgments. As predicted, the information made lighter smokers more optimistic and heavier smokers less optimistic. However, the experimental manipulation had no effect on intention to give up smoking. The difference score (other's risk minus own risk) correlated 0.52 with the single-item comparative risk measure. The former measure showed a small but significant optimistic bias whereas the latter measure showed a small but significant pessimistic bias. The findings are discussed in terms of measurement issues and the implications for interventions designed to influence risk perceptions.