In this population-based study we compared self-esteem, social background, social and academic competence, behavioural problems and lifestyle in 58 obese adolescents (BMI > or =99.6th percentile or > or =30 kg/m2), aged 14-18 y, with 58 sex- and age-matched controls of normal weight. The instruments used were: I Think I Am, Youth Self Report and a lifestyle questionnaire. The obese group was on average, 40 kg heavier than the controls. The obese individuals rated themselves significantly lower in physical characteristics, but in all other aspects of self-esteem, mental health and social and academic competence there were no differences between the two groups. There were significant socioeconomic differences, with more obese adolescents living with only one parent and with the mothers in the obese group having, in general, lower education than those in the control group. This study confirms previous observations that obesity is associated with special socioeconomic conditions in youth, but that obese adolescents do not differ from their normal-weight peers in other aspects of mental health.