Inferior sinus venosus defect is a rare lesion in which there is a large interatrial communication adjacent to the atrial connection of the inferior caval vein. The defect is located posteriorly and inferiorly, outside the confines of the true atrial septum, and partial anomalous pulmonary venous connections are the rule. We underwent surgical repair in four patients with inferior sinus venosus defect and partial anomalous pulmonary venous return. There were three males and one female with an age range from four months to 25 years. A cross- sectional echocardiogram and cardiac catheterization had been performed preoperatively in all patients, but the correct diagnosis had been made in only one case. Surgical repair was indicated due to congestive heart failure, and one patient of 4-month-old needed urgent operation. The repair was accomplished by suturing a untreated autologous pericardial patch to the right of the pulmonary veins, so that the defect was closed and all the pulmonary venous blood was directed to the left atrium. The preoperative knowledge of the unusual anatomy allows the surgeon to repair the anomaly without difficulties. For the patients in whom interatrial communication and anomalous pulmonary venous return are suggested, surgeon has to pay careful attention to the anatomical landmarks to avoid incorrect placement of the patch.