Background:Imaging of the coronary artery by CTA non-invasively has been increased in the recent years. Objectives: To compare the diagnostic accuracy of 16, 64,128, and 320-rows computed tomography angiography (CTA) in patients with suspected coronary artery disease (CAD) using invasive coronary angiography (ICA) as a golden standard. Methods: A retrospective analysis of consecutive 103 patients presenting to a different hospitals for investigation of CAD and then underwent ICA. The accuracy of CTA for detecting CAD was compared with that of ICA. Results: A total of 50 patients proved to have CAD, 8 diagnosed by 16, 17 by 64, 13 by 128 and 12 by 320 rows. At patient level, CTA revealed sensitivity of 66.7%,89.5%,92.9% and 92.3% for 16, 64, 128 and 320 rows respectively. A specificity of 80%,92.3%,90% and 91.7% respectively. PPV was 80%,94.4%,92.9% and 92.3%, and a NPV was66.7%,85.7%,90% and 91.7%. At vessel level the sensitivity was 46.4%,73 .3%,82.4% and 90%. A specificity was 84.2%, 92.2%,92.1% and 93.3%. A PPV was 68.4%,89.2%,90.3%, and 90%. A NPV of 68.1%,79.7%,85.4% and 93.3%. At segment level sensitivity was 46.6%,73%,78.5% and 94.4%. A specificity was 88.1%,92.9%,94.2% and 95.8%. A PPV was 54.7%,88.5%,92.9% and 96.5%, with P