Purpose: The study used the two-factor Theory of Planned Behaviour (TPB) to predict healthy breakfast choices in a sample of adolescents and the extent to which gender, social class and age (school grade) moderated the relationships. Methods: A total of 1735 11- to 15-year-olds recruited from schools in Gothenburg, Sweden, completed TPB questionnaires on choices of high-fibre bread and low fat milk for breakfast. The TPB questionnaires tapped intentions, affective and instrumental attitudes, injunctive and descriptive norms and perceived control and confidence. Two weeks later the adolescents completed a seven-day food diary about food consumed at breakfast. Results: Intentions to consume high-fibre bread and low fat milk were predicted by affective and instrumental attitudes, injunctive and descriptive norms, and perceived confidence. In addition, affective attitudes for bread and descriptive norms for milk were stronger predictors of intentions in the older groups. Consumption of high-fibre bread and low fat milk was predicted by intentions, perceived confidence, and the interaction between age and intentions. Decomposition of the interaction between age and intentions for the two breakfast choices indicated that intentions were significantly stronger predictors of behaviour for the older children. Conclusions: The two-factor TPB provides a reasonable basis for predicting intentions and behaviour in relation to healthy breakfast choices in adolescents and basing interventions to change such behaviours. The importance of personal and parental factors was demonstrated by the fact that attitudes (instrumental attitudes for milk and affective attitudes for bread) and descriptive norms were the strongest predictors of intentions for the two behaviours. In turn intentions were the most powerful determinants of both behaviours. Importantly intentions were significantly stronger determinants of both behaviours in older compared with younger adolescents. This probably reflects both developmental factors and the growing autonomy over healthy behaviour choices that adolescents experience as they grow older. Implications for using the two-factor TPB in relation to health behaviours in children and adolescents are discussed.