We studied the consistency over time of the addictive behaviour dimension measured by its key components, tobacco and alcohol use. Changes in the relationship between the two behaviours in 1977–1993 were analysed using data from the Adolescent Health and Lifestyle Survey, collected biannually by mailed questionnaires from nationally representative samples of 12- to 18-year-old Finns. The number of respondents varied from 2832 to 4275 and the response rate from 77 to 88%. Correlation between the two behaviours was strong (0.67) and stable during the 16 years. A typology of tobacco and alcohol use was constructed (inexperienced, only tried, experimental use of tobacco only, experimental use of alcohol only, smokes only, drinks only, regular user, hard user and other) and changes analysed by logistic regression models. A decrease was observed among the inexperienced group (16 and 18 year olds) and in the experimental use of tobacco only group. A marked increase was observed in the drinks only group. The smokes only group became smaller in the latest surveys. The results suggest that the addictive behaviour dimension should be divided into two subdimensions, a ‘traditional’ one, which is consistent over time and indicated by use of both substances, and a ‘modern’ one, where alcohol use only is present.