AIM: To compare the prevalence of metabolic syndrome (MetS) between women with polycystic ovary syndrome (PCOS) and controls across different age (≤20, 21-30 and 31-39 years old) and body mass index (BMI) (normal weight, overweight and obese) groups.METHODS: We studied 1223 women with PCOS and 277 BMI-matched controls. The prevalence of MetS in women with PCOS and controls was estimated according to four different MetS definitions.RESULTS: In subjects ≤20 and 21-30 years old, the prevalence of MetS did not differ between women with PCOS and controls regardless of the MetS definition, even though women with PCOS were more obese than controls in the ≤20 years old group. In subjects 31-39 years old, the prevalence of MetS was higher in women with PCOS than in controls but the former were more obese than controls. The prevalence of MetS did not differ significantly between women with PCOS and controls in any of the BMI groups (normal weight, overweight or obese) regardless of the MetS definition.CONCLUSION: The prevalence of Mets appears to be primarily determined by obesity and age whereas PCOS per se appears to be a less important contributing factor.