Objective To evaluate the effectiveness of MSCT in the diagnosis of superior sinus venosus atrial septal defect.Methods The MSCT features of superior sinus venosus atrial septal defect in twenty cases were evaluated retrospectively.The following data were recorded:the size and location of sinus venosus atrial septal defect,the anatomy of pulmonary vein,including number of anomalously draining pulmonary veins and their site of drainage,and associated anomalies.Results In all patients,the superior sinus venosus atrial septal defect locates in the extraseptal wall,which normally separates the right upper pulmonary vein from superior vena cava(SVC).And anomalous connection of right upper pulmonary venous and SVC was identified in all the patients.The mean value of the defect diameter was ( 17.1±5.8) mm.Left superior vena cava was identified in 3 patients.In an elderly patient,left anterior descending branch of coronary artery presented significant stenosis.And in another elderly patient with large atrial septal defect,severe pulmonary hypertension was identified by cardiac catheterization.MSCT findings of superior sinus venosus atrial septal defect in 6 cases were finally confirmed by surgical operation.Conclusions Contrastenhanced MSCT was a useful technique for the diagnosis of superior sinus venosus atrial septal defect,which accurately displayed the anatomical characteristics of the associated malformations for preoperative evaluation.