Polycystic ovary syndrome (PCOS) is the most frequent endocrinological disorder among women in the reproductive age. It is by its very nature a heterogeneous juxtaposition of clinical and biochemical features. In women with PCOS, the most common clinical manifestations - obesity, hirsutism and oligomenorrhoea - are associated with insulin resistance, dyslipidaemia, hypertension, vascular dysfunction involving chronic inflammation and also reduced cardiopulmonary function. The focus of this overview is therefore on PCOS comorbidity with the metabolic syndrome, type 2 diabetes and cardiovascular diseases.