Aim of the study is to evaluate whether intentions toward doping use in adolescents could be predicted by the Theory of Planned Behaviour variables (attitudes, subjective norms, perceived behavioural control). Two variables were added to the basic model: past use of ergogenic supplements and a moral disengagement measure. 952 Italian students participated in the study. A multi-group confirmatory approach was considered, testing whether theoretical relations hypothesised in the model were stable across gender and across types of involvement in sport. The model fits the data satisfactorily. Regression coefficients were stable across gender and across different kinds of involvement in sport. All the variables considered significantly predicted intentions. The implications of these empirical findings for programs aimed at preventing doping abuse in adolescence are discussed.