Functional imaging that assesses myocardial perfusion (MPI) plays an important role in the diagnosis of coronary artery disease (CAD).1 CZT-SPECT MPI enables quantitative perfusion assessment with quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR), defined as the ratio between stress and rest MBF. Myocardial flow reserves above 2.0 have demonstrated in PET a very high negative predictive value and reliably exclude high-risk obstructive CAD; severely reduced MFR (2–5 CZT-SPECT MBF and MFR have also demonstrated good diagnostic sensitivity and specificity for CAD diagnosis as compared with criterion standards used in clinical practice.6 However, MFR cutoff values ranged from 1.3 to 2.7, with a mean value of 1.96,7 and a higher cutoff with the D-SPECT than with the Discovery NM530c (2.4 vs 1.8). The mean normal rMBF and sMBF values were reported as 0.9 and 2.3 mL/min/g, respectively. The aim of this study was to report normal MBF and MFR values in very low-risk patients referred for CAD screening with dynamic SPECT enrolled in the CFR-OR trial (clinicaltrials.gov unique identifier NCT03586492), in comparisons with patients experiencing CAD. We excluded patients with 10 years risk of fatal cardiovascular events ≥5% according to the European Society of Cardiology HeartScore, abnormal visual SPECT, abnormal coronary angiography results, diabetes with over 5 years evolution, and typical chest pain. Two patients were excluded because of suspected hidden caffeine intake (no difference between rest and stress MBF). Dynamic SPECTs were acquired using Discovery NM530c cardiac-CZT camera (GE Healthcare, Haifa, Israel) and analyzed with Corridor 4DM software (INVIA, Ann Arbor, MI), using net retention model from Leppo to generate time activity curves (A). All MBF and MFR values are presented without attenuation corrections. Eighty-four patients (31 male) were analyzed. The mean age and BMI were, respectively, 68 ± 9.4 years and 28 ± 5.3 kg/m2. All patients had less than 3 cardiac risk factors, mean 1.9 ± 0.9. The mean 10 years risk of fatal cardiovascular events SCORE was 2.7% ± 1.4%. The mean stress and rest MBF were 1.6 ± 0.6 and 0.6 ± 0.2 mL/min/g. The mean MFR was 2.7 ± 0.7 (B). Comparatively, patients with abnormal visual MPI and/or lesions at invasive coronary angiography had significantly reduced values: 0.7 ± 0.3 mL/min/g, 1.2 ± 0.5 mL/min/g, and 1.9 ± 1, respectively, for rest and stress MBF and MFR (C). Our values are consistent with recent published findings7; however, those available data have been described for high-risk and CAD patients. No previous SPECT data had been published in very low-risk patients. A previous PET study included 14 low-risk patients (13N-ammonia and 82Rb, and reported a lower limit of normal MFR = 2.2 (mean - 2 SD).8 In this study, we first report SPECT MFR values in very low-risk patients, which is critical as dynamic SPECT is a recent technology with potential great impact in cardiac risk stratification and CAD diagnosis thanks to its easier access than PET.