Valproate (VPA) is a highly effective drug successfully employed in several neuropsychiatric diseases. In the last 15 years, an increased prevalence of polycystic ovary syndrome (PCOS) associated with VPA use has been reported in both women with epilepsy and women with bipolar disorders. However, data on this subject are contrasting and it is possible that different factors might play a role in the development of PCOS in these patients. The risk of developing PCOS during VPA treatment seems to be higher in women with epilepsy than in women with bipolar disorders, and this might be due to an underlying neuroendocrine dysfunction related to the seizure disorder. Gynecologists must be aware of the possibility that PCOS in these populations of patients might be related to VPA use, and a careful multi-specialist approach is required for evaluating the risks and benefits of this treatment in the presence of features of PCOS.