New evidence suggests that children with chronic conditions may be predisposed to overweight and obesity. This study provides prevalence estimate of obesity for children and adolescents with select chronic conditions. We analyzed reported height and weight and the corresponding BMI from 46,707 subjects aged 10-17 years collected by the National Survey of Children's Health (NSCH-2003). Our main outcome measure was the prevalence of obesity (defined as >/=95th percentile of the sex-specific BMI for age growth charts), adjusted for underlying demographic and socioeconomic factors. We found that the prevalence of obesity among children 10-17 years of age without a chronic condition was 12.2% (95% confidence interval (CI) 11.5-13.0); the prevalence of obesity for children with asthma was 19.7% (19.5-19.9); with a hearing/vision condition was 18.4% (18.2-18.5); with learning disability was 19.3% (19.2-19.4); with autism was 23.4% (23.2-23.6); and with attention-deficit/hyperactivity disorder was 18.9% (18.7-19.0). Our findings suggest that children 10-17 years of age with select chronic conditions were at increased risk for obesity compared to their counterparts without a chronic condition.Obesity (2009) doi:10.1038/oby.2009.185.