The aim of this study was to determine the strong candidate genes increasing susceptibility to obesity among previously reported obesity-related genes in Korean subjects and evaluate gene-environmental interactions in susceptibility to obesity. The study population comprised of 163 adolescents (95 boys and 68 girls) and their parents (97 men and 96 women).We used multivariable-adjusted logistic regression analysis, and classification and regression tree (CART) analysis incorporating both the genetic (ADRB2 R16G genotype) and environ- mental (overeating, smoking status, and parent’s obese status) variables. The polymorphisms were genotyped with SNP-ITTM assays using the SNPstream 25KTM System (Orchid Biosciences, New Jersey, USA). Arg16 allele of ADRB2 R16G, smoking and overeating were linked to an increased risk of obesity in adults. CART analysis showed that smoking parents who overate and carried the Arg allele, ADRB2 R16G, had an odds ratio (OR) of 11.7 (95% confidence interval (CI), 2.13-64.04) for obesity compared to non-smoking parents who had none of these factors. Among children, the highest risk group for obesity was the overeater with obese parents (OR, 5.20; 95% CI, 1.86-14.53). The results of the study indicate that beta2-adrenoceptor polymorphism may contribute to the development of obesity through gene-environmental interactions. Further replication studies with larger sample size would be needed to confirm our study results.