Background: A comparison of different definitions of metabolic syndrome (MetS) on its prevalence among a sample of urban high-school students in Taipei City in Taiwan was examined. The differences in the discriminatory power and the optimal cutoff points of relevant risk factors were analyzed in this study.Methods: A total of 45,756 health checkup data sets from 2011 to 2014 of high-school students aged between 15 to 17 years were sourced in Taipei city in Taiwan. The database included the students’ gender, age, height, weight, waist circumference (WC), systolic and diastolic blood pressure, as well as biochemical markers such as triglycerides (TG), high-density lipoprotein cholesterol, and fasting glucose (FG) levels. The receiver operating characteristic (ROC) curve statistical approach was used to analyze the discriminatory power and optimal cutoff points of the relevant MetS risk factors. Results: The prevalence of MetS among adolescents in Taipei City in Taiwan was 2.3% and 1.2%, according to the criteria of the modified National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) and the International Diabetes Federation (IDF) respectively. The prevalence increased to 4.3% when this study’s criteria were used. Among the components of MetS analyzed, WC and TG had stronger discriminatory powers, while FG had the weakest. The optimal cutoff point for WC was approximately the 90th percentile, while that for the TG was similar to the criteria of the modified NCEP ATP III. About 44.6% of adolescents had at least one MetS component. Body mass index also had good discriminatory power.Conclusions: The prevalence of MetS differs depending on the diagnostic criteria used. Redefining the cutoff points for the components of MetS in adolescents in different regions, as well as further screening and intervention, is crucial to prevent cardiovascular disease and type 2 diabetes mellitus in adulthood.