A rare anomaly, Cor triatriatum dexter combined with pulmonary stenosis and patent foramen ovale in a 2-years- old female is presented. Abnormal embryologic development of the right sinus venosus valve caused partial membranous septation of the right atrium. Most cases have been recorded at necropsy either as an incidental finding or in association with severe congenital heart disease. In this case, Cor triatriatum dexter was diagnosed preoperatively by cineangiography and echocardiography.