Background: Patients' perception of risk and their lifestyle choices are of major importance in the treatment of common chronic diseases. This study reveals determinants for and knowledge about why people accept or reject preventive medical interventions against heart disease. Methods: A representative sample of 40-60-year-old Danish inhabitants was invited to participate in a web-based survey. The respondents were presented with a hypothetical scenario and asked to imagine that they were at an increased risk of heart disease, and subsequently presented with an offer of a preventive medical intervention. The aim was to elicit preference structures when potential patients are presented with different treatment conditions. Results: About one third of the respondents were willing to accept preventive medical treatment. Respondents with personal experience with heart disease were more likely to accept treatment than respondents with family members with heart disease or no prior experience with heart disease. The willingness to accept treatment was similar for both genders, and when adjusting for experience with heart disease, age was not associated with willingness to accept treatment. Socioeconomic status in terms of lower education was positively associated with acceptance. The price of treatment reduced willingness to accept for the lower income groups, whereas it had no effect in the highest income group. Some 57% of respondents who were willing to accept treatment changed their decision following information on potential side effects. Conclusions: In accordance with our pre-study hypothesis, individuals with low income were more sensitive to price than individuals with high income. Thus, if the price of preventive medication increases above certain limits, a substantial proportion of the population may refrain from treatment. More than half of the respondents who were initially willing to accept treatment changed their decision when informed about the presence of potential side effects. This is an important observation in relation to risk communication, since most side effects occur very seldom, and a skewed assessment of treatment efficacy compared to risk of side effects may refrain some patients from treatment. Thus, more research is needed to better allow patients to compare treatment efficacy with risk of side effects in quantitative terms.