Polycystic ovary syndrome (PCOS) is one of the most controversial endocrine disease, for its clinical and biochemical heterogeneity. Many authors focused on the possible role of genetic, environmental and hormonal factors in the development of the syndrome, but the etiopathogenesis still remains unclear. The diagnostic criteria for the definition of PCOS are as heterogeneous as the disease itself and underwent more than one revision throughout the last years. Ultrasonography has been widely accepted as an important criterion for the detection of polycystic ovaries. Furthermore, Doppler flow analysis of both intraovarian and uterine arteries seems to provide an insight to the pathological state and the degree of progression of the disease. In this review, we provide the state of the art for a correct diagnosis of PCOS, pointing out the capacity of ultrasonography and color Doppler imaging in the early detection of the syndrome and the possibility to obtain additional information about its pathophysiology. Since PCOS patients have higher cardiovascular risk the precocity and the precision of the diagnosis is extremely important to improve the long-term prognosis.