Background: The presence of myocardial ischemia is an important risk factor for an adverse clinical outcome. Revascularizations of stenotic coronary lesions that induce ischemia can improve a patient's functional status. The aim of the present study was to evaluate the diagnostic accuracy of CT coronary angiography in patients with moderate to severe coronary artery lesions in correlation with invasive coronary angiography and fractional flow Reserve (FFR).  Methods: The current study was a prospective analysis of 70 individuals who had coronary computed tomography angiography (CCTA), diameter stenosis was calculated. Then, patients were divided into two groups according to CCTA results, either intermediate coronary artery stenosis (50% to 69% diameter stenosis) or severe coronary artery stenosis (≥ 70% diameter stenosis), and the two groups referred to invasive coronary angiography and distal pressure and aortic pressure were measured and FFR was calculated. This study took place in Mediclinic Al Ain Hospital, Mediclinic Al Madar Medical Center, Al Madar diagnostic center and Medical Heart Center in Al Ain city, United Arab Emirates. Results: Out of 70 patients, 36 (51.4%) underwent PCI to LAD, 13 (18.6%) underwent PCI to LCX, 7 (10%) underwent PCI to RCA and 16 (22.9%) weren't subjected to any procedure. Stenosis in different vessels (LAD, LCX and RCA) was evaluated by CT angiography and invasive coronary angiography, by comparing between the two methods, the stenosis was found insignificantly different. The mean difference in LAD stenosis was 1.6 ± 12.67 (limits of agreement -23.2: 26.4), was -1.4 ± 13.56 (limits of agreement -27.9: 25.2) in LCX and was 3.1 ± 7.51 (limits of agreement -11.6: 17.8) in RCA. The ability of CT angiography and FFR in evaluating the significance of stenosis was comparable. The ability of invasive coronary angiography and FFR in evaluating the significance of stenosis was comparable. Conclusion: In CAD patients with artery stenosis, the stenosis in different vessels (LAD, LCX and RCA) was evaluated by CT angiography, invasive coronary angiography and fractional flow reserve that were insignificantly different. Thus, developing non- invasive methods for evaluation of stenosis is important for practitioners in determining individuals at high risk for advanced ischemia heart disease who might need a more aggressive therapeutic approach and closer clinical follow-up.