To assess youth health behaviours and related quality of life in urban Tunisia, we conducted a cross-sectional survey of a representative sample of 699 secondary-school students. The overweight rate was 20.7%. Most of the sample had an insufficient level of physical activity and were unfamiliar with the recommended frequency of moderate physical activity. Norm-based scores of psychological state were about average, slightly better for boys than girls. Girls perceived themselves to be more stressed than boys. Of all students, 35% declared having smoked a cigarette and 14% having drunk alcohol at least once in their lives. The main sources of health education were mass media (59%) and medical staff (36%).