Purpose Examine the health-related quality of life of 5-6-year-old underweight, overweight and obese children. Methods Our cross-sectional study included 3,227 parent- child dyads from the "Be active, eat right" study. Parents completed questionnaires regarding child and parental characteristics. Health-related quality of life of the child was measured using the Child Health Questionnaire Parent Form 28. Children were classified normal weight, overweight, obese, severely obese, and underweight according to the international age and gender BMI cutoff points. Bootstrap analyses were performed for general linear models corrected for potential confounding variables. Results Severely obese children (b, -2.60; 95 % CI, -4.80 to-0.57, p\0.01) and underweight children (b,-1.11; 95 % CI,-1.85 to-0.39, p\0.01) had lower parent-reported scores on the physical summary scale. On the physical functioning profile scale parents of overweight and severely obese children also reported statistically significant lower scores (p\0.05 and p\0.01, respectively).There were no significant differences regarding the psychosocial summary scale scores between the different weight categories. Conclusion Underweight and overweight children experience impaired health-related quality of life on the physical functioning domain. Physicians, teachers and parents should be aware of the possible negative impact on healthrelated quality of life in underweight and overweight 5-6- year-old children. © The Author(s) 2012.