How will snus use in adolescence influence tobacco use in young adulthood? The main aim of this project is to investigate changes and directions in tobacco use, in particular between use of snus and smoking, and factors associated with reduction or escalation of smoking and snus use between adolescence and adulthood. Baseline risk factors, as previous tobacco and alcohol use, the parents’ use of tobacco, and the adolescents’ plans for own education are considered in the analyses. In particular, in this cohort study, we aim to assess the often asked question of whether snus use at young age is neutral or preventive with respect to future tobacco smoking. On the other hand, snus may also act as a risk factor for smoking, or combined use of both types of tobacco, as young adults. These questions are important to investigate, given the debate on tobacco regulation and policy. Questionnaire data from the health surveys in HUNT3 from young adults who also participated as adolescents in UngHUNT 1 and/or UngHUNT 2 will be applied for from the NTNU-HUNT research centre.