Abstract Objective To determine the health-related quality of life (HRQOL) of overweight and obese multi-ethnic children compared with normal-weight children; and to investigate differences in HRQOL between self- and parent-proxy reports and ethnic groups. Design Prospective cross-sectional study. Setting Out-patient clinic where children and their parents filled out a validated HRQOL questionnaire (KIDSCREEN-52) and height, weight, waist circumference and fat percentage were measured. Subjects Overweight and obese children, aged 8–18 years (mean BMI Z -score 3·2 ( sd 0·6)), from the obesity out-patient clinic. Results Three hundred and eight self- and 213 parent-proxy reported questionnaires were completed. Global HRQOL and the Physical Wellbeing, Moods & Emotions and Self-Perception subscales were markedly reduced in our multi-ethnic obese cohort, relative to the Dutch reference values. Parent proxies reported significantly lower on the global HRQOL and the Physical Wellbeing, Moods & Emotions and Bullying subscales. In Caucasian children, multivariate analyses showed that BMI was associated with the quality-of-life subscales Moods & Emotions, Self-Perception and Bullying. Conclusions HRQOL was markedly reduced in our multi-ethnic overweight and obese out-patient clinic cohort, with significantly lower parent-proxy scores compared with self-reported scores. We believe intervention programmes aiming to improve HRQOL should be directed to both parents and children, while ethnic-specific programmes to enhance HRQOL seem of less importance.