Optimistic biases regarding the risks of smoking were examined among 200 adolescents (aged 12-17) and 203 adults (aged 30-50). Strong majorities of adolescent and adult smokers and nonsmokers agreed that smoking is addictive and causes death for "most people" who smoke. However, for themselves personally, adolescent and adult smokers were more likely than nonsmokers to doubt that they would die from smoking even if they smoked for 30 or 40 years. Furthermore, 60% of adolescent and 48% of adult smokers believed that they "could smoke for a few years and then quit" if they wished, figures far higher than for nonsmokers. Thus an optimistic bias regarding smoking risks appears to be held by both adolescent and adult smokers, especially by adolescents and especially regarding addiction. Implications for smoking prevention programs are discussed.