The promotion of a healthy lifestyle is the main goal of physical education in many countries. However, very little is known about the relationship between different lifestyles and physical activity patterns among young people. The aim of this study was to investigate the relationship between lifestyle and physical activity among 12- and 15-year-old boys and girls in Belgium and Finland. The data came from an extensive comparative study, "Sporting Lifestyle, Motor Performance and Olympic Ideals of European Youth". The subjects in this study were 1439 Belgian and 789 Finnish adolescents. Using factor and cluster analyses, five ways of spending leisure time representing different lifestyles were formulated. Additional descriptors of lifestyle were attitude toward school and Physical Education (PE), the importance of being good academically and in sport, perceived competence, and goal orientation. The results showed that there were significant differences in physical activity between the lifestyle groups and that high physical activity was related to more than one lifestyle group. Those who were only interested in computer games and TV-watching were the most inactive, although many computer game players were also physically active. Perceived physical competence and task orientation were positively related to a physically active lifestyle. It was concluded that if the aim of physical education is to enhance an active lifestyle, then a variety of characteristics should be taken into account in teaching. (Contains 4 tables and 4 figures.)