Background: To assess the accuracy of 3D cardiovascular magnetic resonance (CMR) perfusion imaging for the detection of coronary artery disease (CAD) against fractional flow reserve (FFR) and quantitative coronary angiography (QCA) in patients with reduced ejection fraction (EF). Methods: Out of 447 patients who underwent 3D CMR perfusion imaging (at 1.5 and 3.0 T under adenosine stress and at rest) at 5 European centers, 86 cases with an EF .50% were identified (mean age 64 } 11 yrs, 80% male). Significant CAD was defined as a FFR value <0.8 and a QCA >50%. 86 individuals matched for age, gender and major cardiovascular risk factors, were chosen as the control group. Results: The prevalence of CAD defined by FFR (<0.8) was 59% (EF.50%) vs. 54% (EF>50%), P 5 0.4). In relation to FFR, 3D perfusion imaging yielded a sensitivity of 84.5% (95% CI 76.0.90.4) and specificity of 77.3% (95% CI 66.7.85.3). The sensitivity of perfusion imaging was higher in patients with an EF.50% (90.2 vs. 78.3%, P 5 0.1) whereas specificity showed the reverse (62.9 vs. 90.0%, P 5 0.005) The diagnostic accuracy was comparable in both subgroups (AUC 79.1 vs. 83.7%, P 5 0.25). According to QCA, the prevalence of CAD was 78 vs. 72% (P 5 0.4). Perfusion imaging yielded a sensitivity and specificity of 82.1 vs. 62.9%, P 5 0.01 and 79.0 vs. 95.8%, P 5 0.09 respectively with a high diagnostic accuracy in both subgroups (AUC 82.0 vs. 80.5%). Conclusion: 3D-CMR perfusion imaging yields a high sensitivity and diagnostic accuracy with regards to the detection of significant CAD irrespective of left ventricular (LV) systolic function.  Kulcsszavak: Cardiac magnetic resonance perfusion imaging, Coronary artery disease, Heart failure, Late gadolinium enhancement