Objective. This study examined the prevalence of and trends in childhood overweight and obesity among South Korean children using four different criteria. Methods. Data for 7 879 subjects, aged 2–19 (4 091 boys and 3 788 girls), were derived from four waves of the Korean National Health and Nutrition Examination Surveys conducted in 1998, 2001, 2005, and 2007. We examined the time trends in obesity measures based on criteria suggested by the International Obesity Taskforce (IOTF), the US Centers for Disease Control and Prevention (US CDC), the World Health Organization (WHO), and the Korea Centers for Disease Control and Prevention (KCDC). Results. Differences in the absolute prevalence of childhood obesity among the criteria were relatively great. There were no criteria that recorded consistently higher or lower prevalence of childhood overweight (including obesity) and obesity in both genders and age groups compared with other criteria. No differences in time trends of the prevalence between criteria were detected. Increases in the prevalence of overweight and obesity among boys aged 10–19 were found between 1998 and 2001 but, thereafter, trends toward stabilization were found. No significant increases in the prevalence of both overweight and obesity were detected among males and females aged 2–9 between 2001 and 2007 and among females aged 10–19 between 1998 and 2007. Conclusions. The prevalence of childhood overweight and obesity in South Korea stabilized in the early 2000s; however, further policy efforts to lower the high prevalence of childhood obesity and overweight should be exercised.