INTRODUCTION The aim of this study was to assess the validity of a continuous Metabolic Syndrome score (cMetS) in a nationally representativesample of Iranian children and to identify sex and age-specific optimal cut-off points of cMetS that are associated with MetS. MATERIAL AND METHODS This study was conducted among 3,254 schoolchildren aged 10-18 years. cMetS was derived by aggregating ageand sex-standardised residuals of waist circumference (WC), mean arterial pressure (MAP), glucose, high density lipoprotein-cholesterol(HDL-C) and triglycerides (TG). To determine the optimal cut-off points of cMetS for predicting MetS, receiver operator characteristic(ROC) curve analysis was used with an estimation of the variables' sensitivity and specificity. RESULTS A graded relationship was documented between cMetS and the number of risk factors. Increasing mean values of cMetS with increasingnumbers of components were apparent for both genders. The overall optimal cMetS cut-off point for predicting the presence of MetS was 2.93 [sensitivity= 92%, specificity = 91%, area of the curve = 0.96 (0.95-0.97)]. The values for boys and girls were 2.97 and 3.26 respectively in the total study. CONCLUSION This nationwide study confirmed the validity of the cMetS score in a population-based sample of Iranian children. cMetSappears to be an appropriate index for investigating the association between potential risk factors and MetS in epidemiological researchin Iran.