Magnetic resonance (MR) flow mapping can be used to quantify flow velocity and volume flow in the coronary vessels noninvasively. The close anatomic relationship of the left anterior descending artery (LAD) with the great cardiac vein (GCV) allows imaging of both in one view. We examined the feasibility to discriminate between these two vessels based on the flow pattern and to measure the flow quantitatively. Eleven individuals with a normal LAD and 8 patients with a diseased LAD underwent MR imaging. From MR angiograms using connectivity to the aortic root, differentiation between the LAD and GCV was obtained. Perpendicular to both vessels, phase-contrast velocity mapping was performed to measure phasic and mean volume flow. After correction for cardiac motion of the vessel, GCV flow was found to be mainly systolic and pointing in the inverse direction as the predominantly diastolic flow in the LAD. These criteria appeared valid in all subjects, even in cases of highly stenotic arteries. The volume flow measurements corrected for body surface area were 31 ± 15 ml/min/m2 in the normal LAD (n = 11) and 21 ± 10 ml/min/m2 in the diseased LAD (n = 7). The volume flow measurements in the GCV corrected for body surface area were 23 ± 19 ml/min/m2 in the normal vessels and 19 ± 16 ml/min/m2 in the diseased vessels. In the patient with an occluded LAD and collaterals, the volume flow in the GCV was 7 ml/min/m2. MR is a unique tool for noninvasive simultaneous measurement of the flow pattern and volume flow in the GCV and the LAD, showing a clear distinction between arterial and venous flow.