Pediatric obesity can be defined as BMI > 95th percentile for age and sex from large surveys that were carried out in the past. Using these cut points, over 10% of all children and adolescents are obese, and another 10% are overweight (BMI > 85th percentile). Obesity in childhood is associated with many immediate consequences, including orthopedic, neurologic, pulmonary, gastroenterologic, endocrinologic, metabolic, and cardiovascular disorders. Psychosocial and economic problems also are seen in obese adolescents. Long-term consequences of pediatric obesity include risks for cardiovascular disease and death that are independent of adult body weight. The differential diagnosis of pediatric obesity includes many multi-system genetic syndromes and a limited number of endocrine disorders that include abnormalities in the leptin signaling pathway, but most children with excess body weight do not have an established diagnosis. Treatment is best carried out at specialized centers, and usually involves a program of behavioral modification, caloric restriction, increased activity, and decreased sedentary behaviors. Medication for pediatric obesity cannot be recommended at present outside the context of clinical trials. Gastric bypass surgery is effective, but should be considered a last resort for the child with life-threatening complications of obesity.