Background: Coronary artery disease (CAD) is a major cause of morbidity and mortality. Coronary atherosclerosis is a progressive disease with sudden destabilizing changes leading to plaque thrombosis and reorganization. Aim of work: Quantitatively characterize coronary atherosclerotic plaque composition in patients with CAD referred to Ain shams radiology department (El Demerdash Hospital) by using CT coronary angiography and compare prevalence of different plaque types. Patients and Methods: Seventy-eight patients of CAD symptoms (49 male, 29 female; mean age, 54.8 years) underwent CT coronary angiography (CTCA). Each patient underwent a non-contrast scan to determine the calcium score, then a contrast enhanced ECG gated scan. Coronary plaques were analysed as regard number, type, severity and plaque volumes by using semiautomated software. Results: 14 patients had normal CTCA, 37 patient had significant obstructive lesions, and 4 of them had a totally occluded coronary vessel. A total of 232 coronary vessel plaques were found. The number of patients with multi-vessel disease was significantly higher in diabetic patients verses non diabetics. Noncalcified plaques were more prevalent (than calcified plaques), in patients <55 years, where 56.4% of their plaques were noncalcified, however in patients >55 years only 39.3% of their plaques were noncalcified. Conclusion: Multi-slice CTCA is the non-invasive alternative to intravascular ultrasonography (IVUS) for plaque quantification, it is a reliable technique to detect CAD and estimate the degree of obstruction, number of affected vessels and the pattern of their affection. Using automated software provide the major advantage of higher reproducibility.