To determine the effects of EE/CA (Ethinylestradiol/ Cyproterone Acetate) and EE/CA-metformin treatments on the asymmetric dimethylarginine (ADMA) levels in women with PCOS (Polycystic Ovary Syndrome). Among 43 patients diagnosed with PCOS, one study arm (n=22) was administered (35 µg EE, 2mg CA) and the other (n=21) was administered (35 µg EE, 2mg CA plus 1700mg metformin). Serum ADMA, lipid profile, androgens, insulin, and HOMA-IR (Homeostatic Model Assessment of Insulin Resistance ) values were assessed prior to treatment and after 3 months of therapy. A significant reduction in ADMA levels relative to pre-treatment in the EE/CA+metformin group (1.2±0.4 vs 0.95±0.4, p=0.016) compared to the EE/CA group (1.0±0.5 vs 1.03±0.4, p >0.05). Andogens, insulin and HOMA-IR levels decreased in both treatment groups. All lipid profiles significantly improved in-group EE/CA+metformin while no significant decrease was observed in TG and HDL-cholesterol levels in EE/CA group. Post-treatment levels of HDL-C levels correlated significantly with the reducing ADMA levels in the EE/CA+metformin group (P=0.005, r= 0.602). Adding metformin to EE/CA therapy in PCOS may beneficial endothelium effects associated with reduction of ADMA levels.