Vasomotor reactivity is decreased in terms of cerebral blood flow (CBF) response to hypercapnia in patients with cerebrovascular white matter (WM) lesions. This study evaluated whether vasomotor reactivity is altered during postural change in these patients. We examined 28 consecutive patients with cerebrovascular WM lesions, subgrouped into 19 with Schmidt scale 2 and 9 with scale 3 WM lesions. These patients were compared with 15 age-matched patients with lacunar infarction but without significant WM lesions and 6 controls without cerebrovascular disease. With blood pressure monitoring, brain SPECT scans were done in the supine and upright position using HMPAO as a tracer. The ratio of radioisotope (RI) counts in the frontal and parieto-temporal lobes to those in the cerebellar hemispheres (CBF ratio) was evaluated. In the comparison among the three groups, there were no significant differences in the changes of systemic blood pressure after rising. The baseline CBF ratio in the supine position was also not different among the three groups. After rising, the CBF ratio in each region of interest (ROI) did not change significantly in either lacunar infarction or control groups. By contrast, in patients with WM lesions, the CBF ratio in the frontal lobe decreased after rising (p < 0.0001). In the subgroup analysis, there was a significant increase in blood pressure 1, 2 and 3 min after rising (p < 0.05), with a higher tendency in the scale 3 WM lesion group as compared to the scale 2 WM lesion group. The CBF ratio was decreased in both frontal and parieto-temporal areas in the scale 2 WM lesion group, whereas this was significant only in the frontal areas in the scale 3 WM lesion group. Vasomotor reactivity is impaired in cerebrovascular WM lesions, suggesting a susceptibility to postural changes in these patients.