Background: Coronary artery calcifications comprise one of the most significant factors interfering with the diagnostic accuracy of Multi-Slice Computed Tomography (MSCT) .Despite this fact, measurement of Coronary Artery Calcification (CAC) score using Agatston method is a useful noninvasive test for expecting rare but serious potentially life -threatening Percutaneous Coronary Intervention (PCI) complications, our aim to highlight the role of MSCT in coronary disease severity and CAC score as a predictor tool to determine PCI associated complications. Methods: A prospective study was carried out in period from January 2022 to May 2022, conducted at Radiodiagnosis and Cardiology departments of Zagzig university hospitals, enrolled 60 Patients with 78 significant stenotic calcified coronary lesions diagnosed by conventional coronary angiography and MSCT coronary angiography with total, target vessel and significant lesion CAC scores calculation using Agatston method prior to percutaneous coronary intervention (PCI). Results: Our patients were divided into a lower CAC score cases (CAC score, ≤300, n=12 cases/ 12 lesions) and a higher CAC case (CAC score, >300, n=48 cases/ 66 lesions). The highest vessel CAC score mean is of LAD 100.1± 61.98 followed by RCA then LCX and lastly LM, with only three cases of higher CAC score group developed dissection during PCI. with significant difference between successful and complicated PCI regarding the total, target vessel and significant lesion CAC scores with P value < 0.02 Conclusion: Using MSCT to measure CCS prior to intervention can anticipate PCI problems and improve PCI outcomes