Objective To investigate scanning and reconstruction techniques of multi-slice spiral CT (MSCT) in patients with complex congenital heart diseases (CCHD).Methods One hundred eighty-four patients suffering from CCHD underwent 16-detector MSCT scanning without ECG-gating.Multi-planar reconstruction (MPR),maximum intensity projection (MIP),curved-planar reconstruction (CPR) and volume rendering (VR) were used to reconstruct images.CT findings were compared with those of surgical operation or angiocardiography.Results A total of 616 cardiac deformities were found with MSCT and proved by angiocardiograms or surgical operation.The diagnostic accuracy of extracardiac malformation with MSCT was 100%,of atrial septal defect was 54.65%,and of ventricular septal defect was 78.62%.MSCT failed to display heart valve disease well.Conclusion MSCT can accurately detect extracardiac malformations of CCHD.