Four cases of cor triatriatum in children aged from 4 days to 12 months are described. In one case isolated classical form of the disease occurred, and in the other it was associated respectively to ventricular septal defect, anomalous pulmonary venous connexion and persistence of left superior venae cava. One child had successful surgical correction, two died before surgery could be attempted and one waits operation. Relevant clinical and investigational data are described and the role of echocardiography as an excellent diagnostic tool is stressed. We conclude that isolated form of cor triatriatum can simulate primary lung disease and when associated to other cardiac anomalies it has an earlier diagnosis due to early referral. Surgical results and prognosis depend not only on associated anomalies but also on early diagnosis.