Health education often attempts to influence or persuade through risk-appraisal of impending danger or harm. Risk: appraisal implies cognitive processes concerning the severity of the threatening event and the probability of its occurrence. In two studies we investigated whether risk factors could adequately predict preventive behaviour with respect to cancer. The tint study concerned the health belief model. the second study the protection motivation theory. Protection motivation theory includes the health belief factors but also self-efficacy expectancy. The most important finding is that risk-appraisal does not predict preventive behaviour adequately: outcome expectancy and self-efficacy expectancy should be included in the prediction of preventive behaviour. In general, our findings suggest the superiority of the protection motivation theory to the health belief model in predicting preventive behaviour with respect to cancer.