Within the context of problem-behaviour theory, this study investigated the intra-relationship between attitudes and behaviours towards exercise, sport involvement, violence in sport-related events, eating fruits, smoking and hashish or ecstasy use in a sample of Greek adolescents. Age and gender patterns are considered. Methods: Participants were 5991 Greek school pupils who responded to questionnaires assessing behaviour and attitudes towards health-related behaviours. Results: Positive associations were found between pupils’ reports of violence in sport-related events, smoking and hashish or ecstasy use on the one hand, and eating fruits and participation in sport and exercise on the other. In contrast, small positive association was observed between sport involvement and violence in sport-related events. Attitudes towards health risk behaviours were inversely related to attitudes towards health-promoting behaviours, and attitudes were positively related to corresponding behaviours. Sport involvement and regular exercise decreased but smoking and use of hashish or ecstasy increased with age. More males than females participated in organized sport and violent acts in sport-related events. Males’ involvement in sport violence increased with age. Conclusion: Sport is a suitable context for the promotion of several health-related behaviours apart from exercise. Nevertheless, the present sport structure excludes most young people and is positively linked with sport violence. A less demanding sport context should be provided for the majority of young people, particularly for females. Sport programmes designed to promote health behaviours should be encouraged. More concentrated actions to combat sport violence are required.