['Coronary artery calcium (CAC) is a powerful CAD risk marker when assessed by dedicated calcium scoring CT scan. We assessed diagnostic implications of CAC visible on attenuation correction CT scans (CTAC) from SPECT/CT myocardial perfusion imaging (MPI).', 'Visual presence or absence of CAC was assessed on CTAC in 1047 consecutive patients undergoing SPECT/CT MPI. Accuracy of MPI was assessed in patients undergoing invasive coronary angiography (ICA) within 1\xa0year (n\xa0=\xa0109). Outcomes were identified by retrospective chart review.', 'Prevalence of true positive SPECT/CT MPI studies was greater among patients with CAC on CTAC (70% vs 16%; p\xa0<\xa0.001); prevalence of false positive studies was greater among those without (68% vs 15%; p\xa0<\xa0.001). PPV of MPI was 0.82 in patients with CAC, but only 0.19 in those without. Within median follow-up of 27.7\xa0months, patients with CAC had higher all-cause mortality (6% vs 0.4%; p\xa0<\xa0.001), more late revascularizations (8% vs 0.4%; p\xa0<\xa0.001), and more MI (5% vs 0.2%; p\xa0<\xa0.001). Hazard ratio for all-cause mortality, MI, or late revascularization was 22.7 (p\xa0<\xa0.001) for patients with CAC vs those without.'] Does visual identification of coronary calcifications on attenuation correction CT improve diagnostic accuracy of SPECT/CT myocardial perfusion imaging?