Smoking habits were highlighted in a longitudinal study of 1,230 secondary school students from the Oslo area. In the age group 16-19, 31% of the adolescents were daily smokers, rather more girls than boys. Most seem to start smoking between the ages of 12 and 15. These cohorts were selected for a closer analysis of the importance of modeling the roles of parents and peers. Both boys and girls copy their fathers' smoking habits, but girls also copy their mothers habits. For both sexes, parents' serving alcohol to their children strongly correlated with the childrens smoking habits. Reduced subjective well-being also seems to be important in the case of girls. The conclusion is that modeling roles on parents and peers is important for the development of smoking habits. Girls seem to be more vulnerable than boys to the influence of parents and peers, and there is also some evidence that girls often start smoking as a response to reduced subjective well-being.