The present study used a within-participants design to (a) assess the predictive validity of prototype identification versus intention for adolescents' health behaviours and (b) examine whether control of health behaviour by intention relative to identification is associated with key individual difference variables. Participants were school children (N=136) who completed measures of intention, perceived behavioural control and prototype identification for 14 health-related behaviours at Time 1, and reported their behaviour 2 weeks later (Time 2). A hierarchical regression showed that prototype identification and intention exhibited similar predictive validity in the prediction of adolescents' health behaviour. Importantly, identification contributed an additional 6% to the variance in behaviour, after controlling for intention and perceived behavioural control from the theory of planned behaviour [TPB: Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50, 179-211.]. Additional analyses showed that greater social comparison tendencies, lower agreeableness, greater intellect and less emotional stability were all related to greater control of behaviour by prototype identification. The theoretical and practical implications of these findings are discussed. © 2011 Taylor & Francis.