Decreased myocardial attenuation on contrast-enhanced multidetector computed tomography (MDCT) images can be observed in subjects with myocardial infarctions (MIs). It was hypothesized that myocardial hypoattenuation in MDCT can accurately detect the presence of a healed MI as determined by cardiac magnetic resonance delayed hyperenhancement (CMR-DH). Coronary MDCT and CMR-DH were performed in 42 subjects. Pre- and postcontrast MDCT images were analyzed for the presence of myocardial hypoattenuation, and volumes of MIs were quantified on MDCT and CMR-DH images in a blinded manner. The sensitivity, specificity, and negative and positive predictive values of postcontrast MDCT for the detection of MI were 91%, 81%, 83%, and 90%, respectively. MI sizes by postcontrast MDCT and by CMR-DH were strongly correlated (r=0.87, p<0.0001), although MDCT systematically underestimated MI volume (2.7+/-2.5 vs 25.9+/-19.9 ml, p<0.0001). MI size by MDCT was correlated negatively with the left ventricular ejection fraction (r=-0.62, p=0.03) and positively with left ventricular volumes (r=0.68 to 0.72, p<0.01). In 71% of subjects with MIs by CMR-DH, corresponding areas of hypoattenuation were noted also in precontrast MDCT. In conclusion, healed MIs can be detected as areas of myocardial hypoattenuation on MDCT images with high diagnostic accuracy, although their sizes are largely underestimated compared with CMR-DH. The presence of precontrast hypoattenuation suggests that mechanisms independent of reduced contrast delivery contribute to this finding.