Regional cerebral blood flow (rCBF) and its reactivity to acetazolamide were analyzed in a series of 15 cases of childhood moyamoya disease, using the xenon-133 inhalation method and single photon emission CT (SPECT). Most of the patients had normal mean hemispheric cerebral blood flow (mCBF), comparable to that of age-matched healthy children. However, they had abnormal rCBF distribution and disturbed reactivity to acetazolamide in the territory of the internal carotid artery, especially in the frontal lobe. Surgical revascularization for the anterior circulation, which consisted of STA-MCA anastomosis and indirect synangiosis, dramatically improved these cerebral hemodynamics in the anterior circulation, including the frontal lobe, and reactivity to acetazolamide in the whole brain. These results suggest that surgical revascularization for the anterior circulation should be carried out in order to improve cerebral hemodynamics as widely as possible, especially in the frontal lobe, and may improve cerebral perfusion reserve in the posterior circulation.