BACKGROUND Polycystic ovary syndrome (PCOS) is a complex disorder with variable prevalence and clinical presentation in different populations, which may be mediated by geographical and ethnic background. METHODS We performed a comparison of phenotypic characteristics between 547 Chinese and 427 Dutch women with PCOS and oligo/amenorrhoea attending University Reproductive Centers in China and the Netherlands. RESULTS Chinese women presenting with a clinical diagnosis of PCOS were observed to have a higher incidence of hyperandrogenism (HA) ( P < 0.001) and amenorrhoea ( P < 0.001) compared with Dutch women, but no difference was observed in the incidence of polycystic ovaries (PCOs). Using population-specific cut-off values, Chinese women with PCOS demonstrated a higher incidence of increased BMI ( P < 0.001), waist circumference (WC) ( P < 0.001) and waist–hip ratio ( P < 0.001) than Dutch women. In both groups, HA was associated with increased age, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and serum LH while PCOs correlated with BMI, WC, HOMA-IR, fasting insulin and elevated total testosterone. Associations specific for ethnic background were found between LH and HA, and between both BMI and HOMA-IR, and PCOs. CONCLUSIONS Reproductive and metabolic characteristics differed between the two ethnic groups. Chinese women were found to present more frequently with a phenotype associated with increased risk of metabolic complications later in life, compared with Dutch Caucasian women. Ethnicity seems to determine part of the specific phenotypical presentation of PCOS.