Aim: The aim of this study was to evaluate the diagnostic accuracy of Multi-slice computed tomography (MSCT) in evaluation of coronary artery bypass grafts (CABG).Background: A new generation of MSCT scanners, equipped with more and thinner detector rows, allows for reliable non-invasive evaluation of coronary artery bypass grafts regarding the patency and the presence of significant (≥50% diameter reduction) stenosis.Methods: This study included 33 patients with prior CABG surgery and underwent invasive conventional angiography as a gold standard for evaluation of the coronary artery bypass grafts. According to the MSCT scanner used to perform the CT angiography, the patients were divided into two groups; the first group (10 patients) had MSCT angiography performed using a four-detector row scanner; the second group (23 patients) had MSCT angiography performed using a sixty four-detector row scanner. Patients with irregular heart rate, renal failure, severe respiratory distress, decompensated heart failure and known allergy to iodinated contrast material were excluded from the study. Results: In the first group of patients, MSCT angiography had overall accuracy of 70.83%. In the second group of patients; two grafts had sequential anastomoses while two grafts were excluded from the study because of absence of the reference standard of conventional invasive angiography. So, the total number of examined proximal anastomoses was 56 while the total number of examined graft bodies and distal anastomotic sites was 58. One proximal anastomotic site (1.8%), one graft body (1.7%) and three distal anastomotic sites (5.2%) were non-evaluable by MSCT angiography and considered to be significantly stenotic. Twenty one bypass grafts total occlusions and five significant stenoses were correctly detected by MSCT angiography and confirmed by conventional invasive angiography. The sensitivity, specificity, negative and positive predictive values, and over all accuracy for evaluation of the proximal anastomotic sites were 100%, 97.14%, 95.45%, 100% and 98.21% respectively, for the graft bodies; 100%, 97.14%, 95.83%, 100% and 98.28% respectively, and for the distal anastomotic sites; 100%, 91.18%, 88.89%, 100% and 94.83% respectively. The overall accuracy for evaluation of all segments of the coronary artery bypass grafts was 95.15%.Conclusion: MSCT angiography with the new generation scanners allows for the reliable evaluation of coronary artery bypass grafts with high diagnostic accuracy.