BACKGROUND Injury to patent grafts or cardiac chambers may occur during reoperation after coronary artery bypass grafting. Preoperative spatial localization of bypass grafts with computed tomography may improve the safety of these procedures. OBJECTIVES To characterize patients who undergo CT before repeat operations after previous coronary artery bypass grafting, and evaluate its benefit in terms of surgical outcome. METHODS We compared 28 patients who underwent cardiac gated CT angiography before reoperation (CT group) to 45 redo patients who were not evaluated with CT (no-CT group). RESULTS The two groups were similar in most preoperative and operative characteristics. The CT group, however, included more patients with patent saphenous vein grafts and fewer with emergency operations, acute myocardial infarction and need for intraaortic balloon pump support. During mid-sternotomy, there was no injury to grafts in the CT group, while there were two patent grafts and three right ventricular injuries in the no-CT group. There was no significant difference in perioperative mortality (3.6% vs. 8.9%). The overall complication rate in the CT group was 21.4% compared to 42.2% in the no-CT group (P = 0.07). The only independent predictors of postoperative complications were diabetes mellitus, preoperative stroke and preoperative acute MI. CONCLUSIONS The patency and proximity of patent grafts to the sternum are well demonstrated by multidetector CT and may provide the surgeon with an important roadmap to avoid potential graft injury. A statistical trend towards reduced complications rate was demonstrated among patients who underwent CT angiography before their repeat cardiac operation. Larger series are required to demonstrate a statistically validated complication-free survival benefit of preoperative CT before repeat cardiac surgery.