Objective: The present study was designed to assess physical activity, sedentary behaviours and dietary habits among adolescents in Kuwait and to compare the differences between genders. Design: A cross-sectional study was conducted among secondary-school children who participated in the Arab Teens Lifestyle Study (ATLS), a multi-centre collaborative project. Setting: Secondary schools in Kuwait. Subjects: Adolescents (463 boys and 443 girls), aged 14-19 years. Results: Nearly half (44?6 %) of the boys and three-quarters (76?0 %) of the girls did not meet the recommended daily physical activity levels ($2520 MET-min/week, moderate to vigorous intensity). Nearly all (96?3 % of boys and 96?7 % of girls) adolescents reported spending .2 h/d on screen time, with girls found to spend more time per day watching television (P 5 0?02) and using a computer (P , 0?001). The large majority of the adolescents reported skipping breakfast and not having milk and milk products, vegetables and fruit daily, while nearly two-thirds of the boys and girls had sugar-sweetened drinks on more than 3 d/week. Compared with girls, boys reported consuming more fruit (3?4 v. 2?8 times/week, P 5 0?001), dairy products (4?5 v. 3?6 times/week, P 5 0?001) and energy drinks (1?3 v.