BACKGROUND: For the first time a comprehensive international research-based smoking prevention programme addressing adolescents has been launched in Denmark. The ESFA cohort study started in 1997, and this article presents baseline findings. Factors that relate to the initiation of adolescent smoking are found among the concepts of attitude, social norms, social pressure and self-efficacy beliefs. METHODS: Baseline findings from Danish adolescents (n = 1770) in secondary school (mean age 13.8 years). RESULTS: The cross-sectional baseline data show that the attitude-social influence-efficacy-model proves to be of value in highlighting the associations of adolescent smoking behaviour. Social self-efficacy, peer smoking behaviour and the intention to smoke proved to have the strongest associations with smoking. CONCLUSION: It is recommended that self-efficacy beliefs and the individual intentions to smoke should be included in the future in smoking prevention programmes in Denmark. Furthermore, a distinction between the roles of parents and peers should be emphasized when addressing the social environment of adolescents in health promotion.