To examine the validity of the existing Childhood Obesity Risk Evaluation (CORE) index in a representative sample of 6-15 year-old children and adolescents throughout Greece. Materials and methods: Anthropometric, sociodemographic and perinatal data were collected from a representative panhellenic sample of 5946 children and adolescents and were used for the calculation of the scores in CORE index. The association of the CORE index with obesity by gender and age group was examined. Results: The mean score of the CORE index in the total study sample was 3.06±1.92 points (range 0-11). For the total sample, for each one point increase in the index score the likelihood for obesity prevalence increased by 30% (OR 1.30, 95% CI 1.24-1.36). Both in the total sample and by gender, CORE index scoring of 4 represents the optimal cutoff value upon which the likelihood of obesity in children and adolescents increases significantly. In the total sample, the CORE index has 58.6% sensitivity and 63.6% specificity. Conclusions: The CORE index can predict the likelihood for obesity in children and adolescents aged 6-15 years old with good validity.