We studied whether differences in health behaviour between Eastern and Western Finland have changed between 1977 and 1993 and whether adjusting for socio-economic characteristics changes the relationship between region and health behaviour. The Adolescent Health and Life-style Survey data have been collected biannually by mailed questionnaires from nationally representative samples of 16- and 18-year-olds (n = 27,785). The response rate varied from 79 to 83% by year. According to logistic regression analyses, smoking and physical activity were as prevalent and changes over time similar in both regions. In alcohol, high fat milk and female butter use the East-West-difference persisted over time. Regional differences were mainly explained by socio-economic variation between the two regions.