This paper contributes to the empirical knowledge of determinants of smoking initiation in adolescents. The instrument we used was a structural equation model, which is a powerful tool to analyze causal relationships in nonexperimental studies. We used a school-based sample of 1198 teenagers from Spain. We measured the attitude of the adolescents towards tobacco. Attitudes and smoking status are related. Attitudes become more favorable to smoking, as experimentation with cigarettes progresses and pupils become older. Teenagers who have tried at least one cigarette are on average more favorable to smoking than those who had never smoked. The study's limitations were noted.