Background: Multislice CT is a recent development in thespiral CT that allows ECG-gated complete coronary coverage ina reasonable time.Objectives: To investigate the ability of MSCT coronaryangiography, using the 4 and 8-slice CT scanners to detecthigh-grade coronary artery stenosis and occlusion and toevaluate the vascular conduits in patients with previous CABGoperations.Methods: A total number of 45 consecutive patientsscheduled for elective conventional coronary angiography forknown or suspected CAD were enrolled for retrospective ECGgatedMSCT angiography (intravenous contrast agent, 4 / 8 x1.25-mm slice thickness, 500 ms tube rotation) including 10patients who had coronary stents and 13 patients who hadhad coronary artery bypass grafts. Findings of CT angiographywere compared to those of conventional angiograms.Evaluation was performed on a per segment basis, using theresults of selective coronary angiography as the gold standard.Results: Our study revealed an overall sensitivity of 83%,specificity of 93%, PPV of 80.6%, NPV of 93.5 % and accuracyof 90% for detection of significant stenosis (≥50%) or occlusion.Conclusion: CT angiography permits non-invasivecoronary imaging, particularly at the proximal coronarysegments. However, because of the limited temporal & spatialresolutions and the various artifacts associated with datacreation & reformation, post-processing methods, and imageinterpretation, MSCT angiography is not ready to replaceconventional coronary angiography at this time. In view of thehigh NPV, patients without significant CAD would be selectedaccurately at CT, and hence, avoiding the unnecessaryinvasive coronary angiography.