Background: Regional differences in resting myocardial blood flow (MBF) have been observed in patients with hypertrophic cardiomyopathy (HCM), but their determinants are currently unknown. This study verifies whether MBF at rest in HCM is related to delayed contrast enhancement (DCE) or regional systolic function (or both) as determined by magnetic resonance imaging. Methods and Results: Fourteen patients with HCM were studied. MBF was measured with positron emission tomography by use of oxygen 15-labeled water. DCE and tissue tagging, to calculate end-systolic circumferential shortening (Ecc), were obtained with magnetic resonance imaging. The mean resting MBF was 0.78 ± 0.19 mL · min-1 · mL-1, and there was a trend toward reduced MBF in the septum (0.72 ± 0.11 mL · min-1 · mL-1) compared with that in the lateral wall (0.84 ± 0.29 mL · min-1 · mL-1) (P = .092). The distribution patterns of DCE and Ecc were both heterogeneous, displaying significantly increased enhancement and impaired regional systolic function in the hypertrophic septum compared with the lateral wall (both P < .001). Resting MBF was inversely related to the extent of DCE (r = -0.30, P < .001), whereas MBF was not significantly related to Ecc (r = -0.15, P = .072). Conclusions: Regional heterogeneity of resting perfusion in HCM is related to the extent of DCE but not to regional systolic function.