The article presents data on new possible mechanisms of pathogenesis of polycystic ovary syndrome. In the past years there have been a lot of studies on the effect of vitamin D on the development of insulin resistance and hyperandrogenism. The amount of evidence for of the correlation between vitamin D deficiency and obesity is growing. The search for genetic markers predisposing to polycystic ovary syndrome among vitamin D receptor gene polymorphisms seems quite premising. Considering of detected connections, therapy with vitamin D may be an effective treatment for this disease. In addition to the influence on reproductive function vitamin D is involved in the regulation of circadian rhythm, and it’s disturbance may lead to the development of anovulation. Another important factor in control of sleep and wakefulness cycles is melatonin. It’s participation in development and maturation of follicles by inhibiting of oxidative stress was proved, and the use of melatonin in women as a treatment for infertility helped to improve reproductive function. Thus, further studies of the role of vitamin D and melatonin may allow developing principally new approaches and medical guidelines for clinical practice.