The evaluation of coronary arteries has become easier, with regard to postoperative coronary artery bypass grafting (CABG) evaluation through the development of multidetector computed tomography (MDCT). In this study, MDCT and coronary angiography (CAG) were performed for graft assessment after CABG, and the usefulness and assessment capability of MDCT were examined. We examined the morphology of graft stenosis and obstruction in 63 cases (51 men, 12 women, mean age 66 years old) in whom comparison by MDCT and CAG was possible. We used 49 grafts for LITA and 65 grafts for SVG (mean number of anastomoses 2.8). The graft evaluation was possible in all cases in CAG, but it was difficult to evaluate due to artifacts in 5 cases in MDCT. MDCT is less invasive than CAG and is useful for early postoperative assessment of CABG. Also, MDCT allows evaluation of the anastomotic region which can be difficult to evaluate from many directions in CAG, by building an image by the VR, MIP and MPR method. It was particularly useful for evaluation of the form of the whole graft and anastomotic region form by the curved MPR method. Further advance in the evaluation of coronary and bypass graft will depend on future developments in scaning methods and instrument improvements.