OBJECTIVE To prospectively evaluate changes in brain perfusion computed tomographic (CT) parameters after revascularization of unilateral symptomatic carotid artery stenosis and to determine whether pretreatment perfusion CT parameters can be used to predict changes in cerebral hemodynamics after treatment. METHODS This study was medical ethics committee approved, and written informed consent was obtained from all patients. Thirty-six patients (23 men, 13 women; mean age, 67 years) with unilateral symptomatic carotid artery stenosis underwent multi-detector row perfusion CT before and after revascularization. Mean transit time (MTT), cerebral blood volume (CBV), and cerebral blood flow (CBF) were calculated, and relative values based on the comparison between symptomatic and asymptomatic hemispheres-specifically, relative CBV, relative CBF, and difference in MTT-were derived. The absolute and relative perfusion values before treatment were assessed and compared with posttreatment values. These analyses were performed for the group as a whole by using the t test and after subdividing patients into three tertiles according to the difference in MTT by using the Wilcoxon signed rank test. RESULTS Among the absolute perfusion values, only the MTT in the symptomatic hemisphere improved significantly after treatment (P < .01). All relative values (difference in MTT, relative CBV, and relative CBF) changed significantly after treatment (P < .05). When the patients were subdivided into three tertiles according to difference in MTT, no significant change in any relative perfusion value could be demonstrated in the lowest tertile, only the difference in MTT improved significantly (P = .004) in the middle tertile, and all relative perfusion values changed significantly (P = .002) in the highest tertile. CONCLUSIONS Compared with relative CT perfusion values based on interhemispheric comparison, absolute perfusion CT values are less suited for demonstrating changes in cerebral perfusion after revascularization in patients with unilateral symptomatic carotid artery stenosis.