Quantitative coronary angiography (QCA) is routinely performed before valve surgery for severe acquired valvular disease. This technique is relatively invasive, especially in a population with an average risk for significant coronary stenosis. Multidetector computed tomography (MDCT) coronary angiography allows the noninvasive evaluation of the coronary anatomy. The aim of this prospective study was to evaluate the predictive values of 16-slice MDCT in the detection of significant coronary stenosis (> or = 50%) before valve surgery in patients with severe valvular disease without known coronary artery disease and average risk, in comparison with conventional QCA. Forty patients with severe acquired valvular disease (mean age 70 +/- 8.6 years; 20 women; 27 with severe aortic stenosis) underwent coronary MDCT 2 days before cardiac catheterization with QCA. The mean heart rate was 64.7 +/- 8.8 beats/min (range 41 to 78). Four hundred fifty-eight of 600 coronary artery segments (77.3%) were considered assessable by MDCT. In a per-segment analysis, the sensitivity of MDCT for the detection of significant coronary lesions > or = 50% was 77.7%, the specificity was 98%, the positive predictive value was 42.4%, and the negative predictive value was 99%. The main cause of false-positive or false-negative results or nonassessable evaluations was severe coronary calcification. In a per-patient analysis, in comparison with QCA, MDCT correctly classified 33 of 40 patients (82.5%). In conclusion, in patients with an average risk for coronary stenosis before valve surgery, MDCT coronary angiography detected significant obstructive coronary artery disease, with a 99% NPV.