OBJECTIVE The aim of the present study was to evaluate the diagnostic accuracy in detecting high-grade coronary stenoses in patients with known coronary artery disease (CAD) using multidetector computed tomography (MDCT). BACKGROUND The MDCT systems with electrocardiographic (ECG)-gating permit visualization of the coronary arteries. However, severe calcifications and higher heart rates are known to degrade image quality and limit correct diagnosis. METHODS Sixty-six patients with proven CAD as assessed by conventional coronary angiography (CCA) were studied by MDCT (mean time 24 months postangiography). Total calcium score and all coronary arteries, including distal segments and side branches, were assessed with respect to evaluability, presence of high-grade coronary artery stenoses (>70%), and correct diagnosis. Results were compared to CCA. RESULTS A total of 105 lesions were detected by CCA. The MDCT correctly detected 39 lesions (sensitivity 37%, specificity 99%). The correct clinical diagnosis could be obtained in 24 patients (36%). Artifacts due to elevated heart rates or severe coronary artery calcification were the main cause of degraded image quality inhibiting correct diagnosis. In 21/66 patients (32%) all four major coronary vessel segments could be visualized. A threshold for maximum heart rate and a maximum calcification level were established (65 beats/min and an Agatston Score Equivalent of 335, respectively). A second analysis was made using these thresholds. Of all patients studied, 10/11 (91%) were correctly diagnosed when adhering to these thresholds. CONCLUSIONS When using MDCT as a noninvasive diagnostic modality to assess advanced CAD, it appears to be mandatory to preselect patients in order to achieve reliable results.