Personality traits and risk perceptions were examined as predictors of changes in smoking behavior. Participants (N = 697) were part of a randomized controlled trial of interventions to reduce exposure to the combined hazard of radon and cigarette smoke. Participants with higher perceived risk at baseline for the combination of smoking and radon were more likely to have a more restrictive household smoking ban in place at 12-month follow-up (p < .05). Risk perceptions also predicted reductions in the total number of cigarettes smoked in the home for participants in the video intervention who had high or moderate levels of extraversion (p < .01). Greater perceived risk predicted whether highly or moderately conscientious women quit smoking (p < .05). The moderating effects of personality traits should be considered when evaluating risk-reduction interventions.