BACKGROUND: The incidence of skin cancer has had a rapid increase in Sweden during the last 20 years. Sun exposure is an important preventable risk factor for skin cancer. It is essential to develop interventions to change people's exposure to the sun. The perception of own susceptibility to harm is essential in theories about self-protective behaviour. The aim of the present paper was to examine the associations between different risk perceptions, sun-related behaviour, readiness to change, and optimism bias. METHOD: A total of 722 visitors of a mobile skin cancer screening unit answered a questionnaire in the summer of 2001. The campaign was conducted at five different locations in Sweden. RESULTS: The participants in this study seemed to have realistic believes about the contribution of solar radiation to the risk of developing skin cancer, however, they seriously underestimated skin cancer incidence in the population and the impact of skin cancer on general health. CONCLUSION: People concerned about skin cancer seem to be aware of the fact that sun exposure is an important risk factor for skin cancer, but they fail to use this information in a consistent way to formulate a judgment of their own vulnerability to harm. People need to be informed about the high incidence of skin cancer, the personal risk factors of skin cancer, and the fact that unintentional as well as intentional sun exposure increases the risk of developing skin cancer.