Teratomas are tumors which are composed of tissues derived of more than one germ cell layer; they appear between 3-6 weeks of pregnancy and are present more often in females. A prognosis for life depends on the timely diagnosis of the mass and a possibility of surgical treatment. An article presents a case of a female neonate born with severe respiratory insufficiency. Antenatal ultrasound at 19-20 and 30-31 weeks exposed the myoma of the uterus and a probability of large birth weight. Immediately after birth a neonate requested urgent intubation, artificial lung ventilation, intensive therapy for hemodynamic stabilization. The thoracic surgeon suspected the presence of cystic adenomatous malformation upon the chest X-ray and clinical observation data and defined expectant management and prolongation of intensive therapy. Autoptical evidence is a large mediastinal teratoma 10×8×5 cm, weight 135.0 gram, moderate secondary hypoplasia of lungs. Histological processing revealed mass lesion of the anterior mediastinum in a capsule, which was presented with immature discohesive mesenchyme with lymphoid assembly, brain tissue and multiple cysts of different size with inclusions of cartilage tissue. Effective correct and precise antenatal visualization, which can defined the type of maternity hospital, postnatal MRT and timely provided therapy intervention surgical mass removal including — these are key factors of successful management newborns suffering from anterior mediastinal teratomas. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of these Institutes. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: newborn, mediastinal teratoma, diagnostics, therapy.