The so called scimitar syndrome is a congenital malformation characterized mainly by the anomalous venous return of the right lung in inferior vena cava. Many structure of the lung may be involved. Usually lobation and bronchial distribution are abnormal, the right pulmonary artery is hypoplastic or absent, a partial anomalous artery from aorta (pulmonary sequestration) may be present, the entire lung is small and various degree of displacement of the heart to the right is detectable. Associated congenital heart defects may also be present. The name of the syndrome comes from the presence of this vessel (scimitar's sign) on routine chest x-ray. This paper describes the clinical and angiographic reports of four cases, which may represent, according a unique embriological interpretation, a different instances of this syndrome. The anatomic characteristic, the sign of scimitar, could be also absent, as in cases 2 and 3. In the case 2 there was complete absence of right pulmonary artery and in the case 3 a severe hypoplastic right pulmonary artery with unique small venous return in left atrium. The authors opinion is that all the anomalies of lung vascular connections, that result from interference with the normal growth of the lung bud, its separation from systemic vascular channels, and the establishment of the lesser circulation should be included. Because the different components of thie malformation can be present in various combination, the sign of scimitar is not pathognomonic to define the syndrome.