OBJECTIVE: Patients with polycystic ovary syndrome (PCOS) diagnosed with the 1990 criteria (i.e. presence of oligo- and/or anovulation (ANOV) and hyperandrogenemia and/or hyperandrogenism (HA) with or without polycystic ovaries (PCO)) appear to have a more adverse metabolic profile than patients diagnosed with the additional criteria introduced in 2003 (i.e. presence of HA and PCO without ANOV and presence of ANOV and PCO without HA). Vaspin is a novel adipokine that appears to preserve insulin sensitivity. We aimed to assess serum vaspin levels in patients with different PCOS phenotypes.METHODS: We studied 100 patients with PCOS diagnosed with the 1990 criteria (group I), 100 patients with PCOS diagnosed with the additional 2003 criteria (group II) and 50 healthy controls.RESULTS: Serum vaspin levels were higher in groups I and II than in controls (p < 0.001 and p = 0.001, respectively) and in group I when compared to group II (p = 0.045). In patients with PCOS, serum vaspin levels were independently correlated with BMI (p < 0.001) and the homeostasis model assessment of insulin resistance (HOMA-IR) (p = 0.002).CONCLUSIONS: PCOS is associated with elevated serum vaspin levels. This increase might represent a compensatory mechanism to preserve insulin sensitivity. Moreover, serum vaspin levels reflect the severity of PCOS and are significantly increased in its 'classical' phenotypes.