We sought to evaluate the role of non-invasive Multidetector computed tomography angiography (CTA) in the assessment of the causes of unstable angina. Background: Detection of coronary artery disease (CAD) using invasive coronary angiography needs extended time, contrast load, and high radiation exposure. Methods: 160 slices CTA was performed in 50 patients (38 men, mean age 55.48 ± 10.88years) symptomatic patients diagnosed as unstable angina. In this study, the mean coronary artery calcium score (CACS) was 204. Statistically higher CAC was found in patients ≥ 60 years old than those < 60 years. Female patients, hypertensives and diabetic patients show slightly higher (but not significant) level of CAC. Among 50 patients complaining of unstable angina we found 11 patients having normal CTA, four having dense coronary calcification, 21 having non-significant obstructive lesions, and 14 patients having significant CAD. We found significant relation between calcium score and the significance of CAD. We detected 70 plaques (29 of them caused significant stenosis) distributed in all coronary arteries. The most commonly affected artery was the LAD, followed by LCX then RCA and the small branches had only 14 plaques. According to the type of plaques, 45 plaques were mixed, five plaques were calcified and the last 20 were soft plaques. We found no significant difference in the significance of stenosis was detected in relation to the number of vessels affected. Patients were classified into Low, Intermediate, and High probability of CAD. We found significant relation between the pre-test probability and the significance of CAD. Conclusions: Multi-detector CTA allows accurate non-invasive assessment of patients presented with unstable angina.