Background: Invasive coronary angiography (ICA) is the accepted reference standard for the assessment of coronary artery stenoses because of its unprecedented temporal and spatial resolution and the ability to perform therapeutic interventions in the same session. Although the associated risk for serious complications is small. The inconvenience for the patient and economic deliberations have strengthened the search for a non-invasive alternative. Current multi-slice computed tomography (MSCT) scanners provide promising results in the assessment of coronary artery disease (CAD). Coronary  CT angiography  using 64-slices has been shown in studies to have a high accurancy when using conventional coronary angiography as the reference standard. The aim of this study was to Evaluate the different diagnostic aspects of non-invasive computed tomography (CT) coronary angiography is ischemic heart diseased patients and  its cost benefit  in comparison to invasive coronary angiography in diagnosis of  various Coronary Artery diseases  (CAD ). Methods: This study was conducted on 20 patients suffering from syptoms related to coronary artery diseases CAD. Patients had undergone ECG gated MDCT coronary angiography in CT unit in Radiology Department of National Heart Institute NHI and were analyzed from PACS  (Syngovia acquisition system). This study included patients for detection of all sorts of  coronary artery diseases compared to the results of invasive coronary Angiography attached with the patients including patients had been subjected for previous CABG operations. Results: In the present study There mean age of patients was 58 ±8.1 years. and 16 patients (80%) were males and 4 patients (20%) were female. According to Risk factors of CAD in study population Diabetes mellitus was founded in 13 patients (65) % , Hypertension in 9 patients  (45)%, Hyperlipidemia in 14 patients (70)%, Current smoker in 15 patients (75)%, Family history of CAD in 11 patients  (55)%, and Obesity in 3 patients  (15)%. In our patient population, the medical data  Heart rate (beats/min) was  67 ± 8.4 and Calcium score (Agatston) was 307.4 ± 57.1, while  Prior myocardial infarction was founded in 5 patients (25%) and Previous PCI in 4 patients (20%). One patient (5%) has previous CABG. 40% of our study population showed  coronary arteries' Anomalies. Acute angle of RCA was showed in 15% patients, RCA arising from LAD in 10% of patients, Posterior oriented origin of LAD from LCC in 5% of patients and  Accessory LAD arising from RCA in 10% of patients. Validity of MDCT angiography in diagnosis of CAD, it showed a dependable accuracy when referred to interventional Catheter Coronary angiography as a gold standard (93.06%) and the most accurate findings was to Left Main Trunk artery. Conclusion: The use of noninvasive 64- slice CT coronary angiography as a vascular imaging technique can be performed rapidly and safely for the assessment of many different pathologies involving coronary arteries with  a high diagnostic accuracy