Background. Adipose tissue synthesizes various adipokines such as resistin, adiponectin and visfatin, which have an effect on insulin resistance. This study was designed to show the effect of metformin, one of the most important drugs used to reduce insulin resistance in patients with polycystic ovary syndrome (PCOS), on these adipokines. Methods. The study group consisted of 24 women with PCOS and 25 healthy, age- and weight-matched, normally menstruating women. Hormone and lipid profiles, visfatin, adiponectin and resistin were measured in all cases, before and after metformin treatment. Results. Serum visfatin levels were found to be significantly higher in patients with PCOS, compared to controls. Following metformin treatment, a significant decrease was observed in visfatin levels compared to the baseline. A positive correlation was found between serum visfatin levels and BMI, waist circumference, HOMA, insulin and triglyceride levels. No statistically significant difference was observed in terms of serum adiponectin levels in women with PCOS before and after treatment, or in healthy controls. Serum resistin levels were significantly reduced by metformin treatment. Conclusion. These findings suggest that visfatin may be related to the obesity and insulin resistance that is frequently encountered in patients with PCOS. A reduction in serum visfatin and resistin levels was shown with metformin treatment, in patients with PCOS.