PURPOSE: To compare the metabolic characteristics of obese and non-obese young women with polycystic ovary syndrome (POS) from the Brazilian Southeast. METHODS: This was a cross-sectional study conducted on 218 women of reproductive age with a diagnosis of POS - 90 non-obese women (BMI between 18.5 and 29.9 kg/m2), and 128 obese patients (BMI <= 30 kg/m2) selected at the time of diagnosis. The frequency of insulin resistance (IR), glucose intolerance (GI), metabolic syndrome (MetS) and type 2 diabetes mellitus (DM2) and mean values of total cholesterol (TC), triglycerides (TG), high-density (HDL) and low-density lipoproteins (LDL), were compared between obese and nonobese patients with POS. The two groups were also compared in terms of clinical and hormonal characteristics (follicle stimulating hormone, prolactin, thyroid stimulating hormone, total testosterone, dihydroepiandrostenedione sulfate, and 17-hydroxyprogesterone). Statistical analysis was performed using the SAS 9.0 software. Quantitative variables were compared by the Student 'st-test (data with normal distribution) or by the Mann-Whitney test (non-parametric distribution). Qualitative variables were compared by the Fisher test. The level of significance was set at 5% (p<0.05) in all analyses. RESULTS: The frequency of IR, GI and MetS was significantly higher in obese than non-obese patients with POS (66.7, 29.9, and 63% versus 24.7, 12.2, and 16.4%, respectively). Obese patients had higher TC and TG levels (189.8 similar to 35.8 mg/dL and 145.4 similar to 71.1 mg/dL, respectively) than non-obese patients (172.1 similar to 38.4 mg/dL and 99.3 similar to 54 mg/dL, respectively). Both groups had mean HDL levels below 50 mg/dL. CONCLUSIONS: Young obese women with POS have a higher frequency of IR, GI and MS than non- obese. However, the occurrence of metabolic disorders is elevated also in the non-obese patients, suggesting that the presence of the syndrome may favor the development of metabolic comorbidities with potential medium-and long-term repercussions.