The present study compared how well four modes of action control (intentional, habitual, reactive and stereotype activation) explain adolescents' cigarette smoking, and examined whether individual differences in self-regulation (locomotion and assessment tendencies; Higgins, Kruglanski, & Pierro, 2003) moderate the behavioural impact of the respective modes. Findings from a prospective questionnaire survey showed that (a) willingness, prototype perceptions and past behaviour--but not intention--predicted smoking behaviour, and explained 63% of the variance, and (b) the assessment mode of self-regulation moderated the past behaviour-future behaviour relation such that past behaviour had less impact on future smoking behaviour at high levels of assessment. These findings suggest that adolescents' smoking is controlled by stereotype activation, habitual and reactive processes. Implications of the results for designing effective adolescent smoking cessation programmes are considered.