BACKGROUND Coronary artery bypass graft (CABG) surgery is the standard of care in the treatment of advanced coronary artery disease, and its long-term results are affected by the failure of bypass grafts. The aim of the present study was to evaluate the early patency rate in coronary bypass grafts. METHODS A total of 107 consecutive patients who underwent CABG were included in this study. Early graft patency was evaluated via computed tomography (CT) angiography in the first week after surgery. RESULTS There were a total of 366 grafts, comprised of 250 venous grafts and 116 arterial grafts. Multi-slice CT detected acute graft occlusions in 32 (8.7%) of all the grafts, including 26 (10%) of the 250 venous grafts and 6 (5%) of the 116 arterial grafts. The patency rates obtained were 97.3% for the left internal mammary (IMA) grafts, 50% for the radial artery grafts, and 50% for the right IMA grafts. Additionally, 107 (96.4%) grafts to the left anterior descending artery (LAD) were classified as patent, whereas 1 (30%) of the 3 grafts in the left circumflex (LCX) region and 1 (50%) of the 2 grafts in the right coronary artery (RCA) territory were found to be occluded. In the venous category, 8 (13.7%) of the 58 grafts to LAD were found to be occluded. In the LCX region, 9 (8.5%) of the 106 grafts were classified as occluded, while the remaining 97 (91.5%) grafts were patent. The venous grafts to RCA were occluded in 9 (10.4%) of the 86 grafts. Amongst the multiple preoperative, intraoperative, and postoperative factors, pump time was significantly longer in the patients with occluded grafts than in those with patent grafts (P=0.04). CONCLUSIONS The IMA grafts had the highest early patency rate amongst the coronary bypass grafts. However, the other arterial grafts were associated with a high rate of acute occlusions.