Background/Aim. Proper nutrition and regular physical activity are essential parts of a adolescent's overall health. The aim of this research was to evaluated eating and physical activity behaviours and habits, nutritional and food knowledge, beliefs and self-efficacy related to diet and health of the adolescents of the city of Belgrade, Serbia. Methods. A dietary questionnaire previously constructed and tested in adolescent population from Italy was self-administrated. We evaluated eating habits, physical activity, meaning of healthy and unhealthy dietary habits and food, self-efficacy, barriers affecting food choices, nutritional and food safety, and body mass index (BMI) of the adolescents. The sample included 707 adolescents, the mean age of 15,8 ± 2 years enrolled in the first grade at several high schools in Belgrade. Results. Only 27% of the adolescents had satisfactory eating habits; 31% have a very active lifestyle; 7% good nutritional knowledge and 6- 12% satisfactory food safety knowledge and hygiene practices. Conclusion. Significant deviations from recommendations for healthy lifestyle was noted in adolescents’ habits, knowledge and practice. It is therefore necessary to develop and organize programs for promotion of healthy behaviours adapted to the adolescents’ needs. [Projekat Ministarstva nauke Republike Srbije, br. III47015]