Metabolic syndrome (MS) is frequent clinical condition in patients with hypertension. Primary aldosteronism (PA) is a common form of secondary hypertension. This study was aimed at investigating the prevalence of the MS and its components in the two major forms of PA, in unilateral aldosterone-producing adenoma (APA) and bilateral aldosterone overproduction because of idiopathic hyperaldosteronism (IHA). The diagnosis of the particular form of PA was based on adrenal venous sampling and/or successful surgery confirmed by histopathological examination. We analyzed clinical and laboratory data from 100 patients with PA (50 patients with IHA and 50 patients with APA) and from 90 patients with essential hypertension (EH). Metabolic profiles of patients with bilateral form of PA (because of IHA) were similar to EH, but differed from those in patients with unilateral form of PA (APA). The prevalence of the MS (62% in IHA, 34% in APA and 56% in EH), the body mass index value (30±4 kg m(-2) in IHA, 27±5 kg m(-2) in APA and 29±5 kg m(-2) in EH) and triglycerides levels (1.9±0.9 mmol l(-1) in IHA,1.4±0.8 mmol l(-1) in APA and 2.01±1.39 mmol l(-1) in EH) were all significantly (P<0.05) higher in IHA compared with APA patients. Metabolic profile of patients with bilateral form of PA (because of IHA) is similar to EH in contrast to unilateral form of PA (APA).