Childhood obesity is directly related to cardiovascular disease (CVD) risk factors, but there is limited information on their relation in Korean children and adolescents. The authors investigated the association between obesity and CVD risk factors among 2,272 Korean boys and girls aged 10-18 years, who participated in the Korean National Health and Nutrition Examination Survey in 1998 and 2001. Obesity was defined by body mass index cutoff points provided by the US Centers for Disease Control and Prevention. The prevalence of obesity increased significantly from 5.4% in 1998 to 11.3% in 2001 (p < 0.0001). Korean obese children and adolescents in 1998 and 2001 had 4.6- and 4.9-fold risks for systolic hypertension, 4.2- and 2.8-fold risks for high levels of total cholesterol, 9.4- and 2.7-fold risks for high levels of low density lipoprotein cholesterol, 4.1- and 3.7-fold risks for low levels of high density lipoprotein cholesterol, and 5.3- and 2.8-fold risks for high levels of triglycerides, compared with their normal-weight counterparts (p < 0.05 in all). Approximately 60% of Korean obese children and adolescents had at least one CVD risk factor. These findings suggest that Korean obese children and adolescents have an increased risk of CVD.