Background The relationship between the signal from retrograde venous flow on magnetic resonance angiography (MRA) and retrograde upward flow from the left brachiocephalic vein has not been explored. Purpose To reveal the frequency of jugular venous reflux using MRA and nuclear venography in patients being evaluated for cerebral volume and blood flow. Material and Methods A total of 229 patients with cognitive disturbance who had undergone brain magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) on the same day to evaluate cerebral blood flow were evaluated. Jugular venous reflux was measured on MRA and nuclear venography, which was conducted just after injection of N-isopropyl-¹²³I-p-iodoamphetamine for the SPECT study. Results MRA showed jugular reflux in seven patients on the right side, and in 22 on the left. Nuclear venography showed jugular reflux in six patients on the right side, and in 20 on the left. Conclusion Jugular venous reflux was observed mostly on the left side. Retrograde flow was observed on both MRA and nuclear venography in half of the cases, with the rest only on one of the modalities.