Recent findings of a direct association of obesity and impaired health-related quality of life (HRQOL) in children suggest a need for early weight-management interventions that address psychosocial issues and lifestyle. Our aim was to compare the effects of exercise, diet, or diet + exercise on HRQOL in obese children. We hypothesized that HRQOL will improve as a result of the weight-loss intervention and will be correlated with the amount of weight loss achieved by each of the intervention groups. A total of 162 children aged 6 to 11 years with a body mass index (BMI) exceeding the 95th percentile were randomly allocated to a 12-week regimens of diet, exercise, or diet + exercise. Weight, height, and percent fat mass were measured, and parents completed the Pediatric Quality of Life Inventory (PedsQL) 4.0 at baseline and at the end of the intervention. The reductions in BMI were significantly greater in the diet and diet + exercise groups than in the exercise group. Pediatric Quality of Life Inventory scores improved significantly, with no differences among the groups. A greater reduction in BMI occurred in children whose parents completed the PedsQL at baseline (n = 105) than in children whose parents did not (n = 15) (-1.8 +/- 1.3 vs -1.0 +/- 1.5; P = .048) and in children whose parents completed the PedsQL at the end of the intervention (n = 73) than in children whose parents did not (n = 47) (-2.0 +/- 1.3 vs -1.3 +/- 1.3; P = .013). Weight-management programs that promote a healthy eating and physical activity can serve as an effective tool to improve the low HRQOL of obese children. Parental compliance is an important factor and may be assessed by the parents' cooperativeness in completing questionnaires.