Introduction. Criss-cross syndrome is a rare congenital heart disease with an incidence of 8 cases per 1 million newborns. The purpose of the work is to demonstrate a rare CHD, a criss-cross heart diagnosed postnatally. The purpose of the work was to demonstrate a rare CHD, a criss-cross heart diagnosed postnatally. Materials and methods. A clinical observation of a newborn child with a rare congenital heart defect is presented. Medical documents with the results of clinical examination (physical examination) and instrumental examinations (X-ray examination, echocardiography, computed tomography) were used for analysis. Results. A child with a rare congenital heart defect (CHD) – criss-cross heart with discordant atrioventricular connections, transposition of the great vessels and preductal aortic coarctation was monitored from the time of delivery until surgical treatment. This malformation was diagnosed postnatally, based on the characteristic clinical symptoms of the detailed segmental analysis of the ultrasound picture of the heart, which is presented as illustrations. Timely diagnosis allowed the choice of adequate medication and surgical tactics of treatment, and the diagnosis was confirmed by computed tomography. Discussion. It is important for the clinician to remember that rare congenital heart diseases cannot always be diagnosed antenatally, and with the results of screening indicating the presence of more common malformations, the real postnatal heart picture may differ significantly. An additional difficulty is the differential diagnosis of the described malformation due to the rare anomalous mutual arrangement of the anatomical structures. Conclusion. Detailed segmental analysis during echocardiography immediately after birth reveals the main diagnostic marker of criss-cross syndrome – inability to simultaneously visualize all four heart chambers and both atrioventricular valves from a four-chamber position.