Resistin, an adipocyte-secreted hormone, has been associated with obesity, insulin resistance and type 2 diabetes mellitus (T2DM) in some, but not all, rodent models. In humans, the exact function of resistin is unkown. Because 3’- untranslated region (3’-UTR) single nucleotide substitutions (SNPs) have been shown to affect gene expression, we examined the EX4-44G→A SNP in the 3’-UTR of exon 3 within the resistin gene. The objective of this study was to investigate, for the first time in a Turkish study group, whether the 3’-UTR EX4-44G→A variation in the resistin gene influences the development of T2DM, obesity and insulin- related phenotypes. We analyzed the genotype frequencies of the EX4-44G→A polymorphism of the resistin gene in 116 type 2 diabetic and 102 normal subjects. Serum lipids, obesity-related and insulin-related phenotypes were analyzed. No significant difference for genotypic frequencies were observed for the BseRI restriction site in type 2 diabetic patients as compared to controls. Waist-to-hip ratio, BMI, body fat and apoAI levels were found to be affected by resistin genotype. In the control group, BMI (p < 0.01), HIS (p < 0.05) and BF (p < 0.05) levels were found to be elevated, whereas HOMA β-cell index (p < 0.01) and apo AI (p < 0.05) levels were found to be decreased in GG genotype carriers. In the diabetic group, the GG genotype carriers were found to have higher BMI levels (p<0.001), waistto- hip ratio (p < 0.05), body fat (p < 0.01), HOMA (p < 0.001) and fasting insulin (p < 0.05), but lower HbA1c levels in comparison to GC + AA carriers. These data suggest that, in the Turkish study group, the EX4-44G→A polymorphism of the resistin gene is associated with insulin and obesity-related phenotypes.