Obesity, physical activity, and sedentary behavior in childhood are important indicators of present and future health and are associated with school-related outcomes such as academic achievement, behavior, peer relationships, and self-esteem. Using logistic regression models that controlled for gender, age, ethnicity/race, and socioeconomic status, we investigated the likelihood that youth with learning disabilities (LD) and attention-deficit/hyperactivity disorder (ADHD) are obese, physically active, and sedentary using a nationally representative sample of 45,897 youth in the United States from 10 to 17 years of age. Results indicated that youth with comorbid LD/ADHD were significantly more likely than peers without LD or ADHD to be obese; that youth with LD only, ADHD only, and comorbid LD/ADHD were significantly less likely to meet recommended levels of physical activity; and that youth with LD only were significantly more likely to exceed recommended levels of sedentary behavior. Medication status mediated outcomes for youth with ADHD. We offer school-based recommendations for improving health-related outcomes for students with LD and ADHD.