The prevalence of smoking among adolescents has stopped declining in spite of all preventative efforts. There is a need for further knowledge and understanding of why adolescents initiate and continue tobacco use. The aim of the present study was to investigate important facets of adolescents' tobacco use, such as their reasons for smoking, and their smoking patterns in relation to smoking habits in the family and the social environment. This study was part of a larger one that used a descriptive, cross-sectional design with questionnaires to 216 pupils in grade 5 (11 years of age) and 225 pupils in grade 8 (14 years of age) in a south-western county in Sweden. Thirteen per cent of the pupils in grade 8 were regular tobacco users. Smoking habits by relatives, especially siblings, influenced tobacco use by adolescents. An association was found between smoking by adolescents and mother's employment, and between the smoking status of girls and family status. The pupils valued their parents' opinions, and wanted parents and other adults to take a clear stand against tobacco. The present study reinforces the importance of norm setting by parents and siblings for adolescents' tobacco use. Preventive measures may be more appropriately directed towards those with the highest risks, i.e. pupils with smoking siblings and smoking peers.