Since the late 80-ies of XX century, due to the expansion of laboratory capacity genetics, amount of new genetic disease has increased significantly. Clarification of the etiopathogenesis of the disease is of great importance to address the issue of disease prognosis, therapy and prognosis of the most important thing for parents about the possibility of the birth of their healthy baby. Therefore, caution is so important neonatologist, a thorough history and careful examination of the patient. The article is devoted and little-known wide range of medical problems - diagnosis and treatment of a rare genetic condition Prader-Willi syndrome in newborns admitted to the neonatal pathology and premature babies Perinatal Center №1 “RH №1-NCM” in the period from 2013 2016. We present our 4 cases of laboratory-confirmed Prader-Willi syndrome. On the first stage of nursing infants were suspected neurological conditions with muscular hypotonia, inhibition of unconditioned reflexes, ie, Neonatologist missed. The syndrome has characteristic symptoms, on the basis of which a neonatologist, pediatrician, neurologist, geneticist may be suspected in the newborn disease Prader-Willi. Flaccid syndrome child who manifested suppression of consciousness, faint, brief cry, difficulty in feeding, the oppression of the majority of congenital reflexes, diffuse muscle hypotonia, decreased spontaneous motor activity. The characteristic phenotype: light skin and hair, dolihotsefalicheskaya head shape, narrow high forehead, microgeny, gothic sky, bird-like face, palpebral boys, girls, almondshaped eyes cryptorchidism boys, girls hypoplasia of the clitoris and the labia minora. The diagnosis was confirmed in all newborns tsitogenetichkim molecular analysis (nuc ish del (15) (q11.2q11.2) (SNRPN) [200]) and found a deletion in a gene SNRPN 100% of the interphase nuclei.