Background: The prevalence of pediatric obesity has increased over the past several decades worldwide and in Korea. Childhood obesity has become a serious social problem.Current Concepts: Diagnosis of obesity is based on body mass index (BMI) in children and adolescents aged ≥2 years. Overweight and obese are defined as BMI ≥85th percentile to <95th percentile and BMI ≥95th percentile, respectively, corresponding to sex and age. Obesity is further classified as Class I (BMI ≥95th percentile to <120% of 95th percentile), Class II (BMI ≥120% of 95th percentile to <140% of 95th percentile), and Class III (BMI ≥140% of 95th percentile). Waist circumference and waist-height ratio are used to evaluate abdominal obesity. Pediatric obesity can cause childhood comorbidities, including type 2 diabetes, dyslipidemia, non-alcoholic fatty liver disease, and hypertension. Adult obesity, cardiovascular diseases, and other adult comorbidities, together with increased medical costs are additional consequences of pediatric obesity.Discussion and Conclusion: Prevention, diagnosis, and proper management of pediatric obesity are important.