Cor triatriatum is a rare congenital heart disease. In the calssic form the left atrium is divided into two chambers by a fibromuscular diaphragm covered by endocardium. The dorsal chamber receives the pulmonary veins, and the ventral chamber gives rise to the left atrial appendage and leads to the mitral valve. Even though the calssic case of cor triatriatum clinically looks like pulmonary venous obstruction, the association, location, and size of the ASD, as well as other cardiac anomalies, may influence symptoms, making the diagnosis difficult. The diagnosis of cor triatriatum is made chiefly from two-dimensional echocardiography and transesophageal echocardiography. The diagnosis can be established by the surgical exploration. In this paper we will report two cases of non-obstruction or triatriatum and review of literature was made.