Xenon-enhanced computed tomographic measurement of cerebral blood flow in patients with chronic subdural hematomas. We compared clinical symptoms with extent of brain shift on computed tomographic (CT) scans and quantitative and three-dimensional measurements of cerebral blood flow (CBF) on xenon-enhanced CT scans in 10 patients with chronic subdural hematomas. Five patients had only headache and minimal or no brain shift on a CT scan. The other five had hemiparesis and/or mental disturbance in addition to headache and moderate or severe brain shift on a CT scan. The mean hemispheric CBF decreased about 7% in patients with headache and about 35% in patients with hemiparesis and/or mental disturbance. It decreased also on the side without the hematoma. The CBF reduction was always more pronounced in the putamen and thalamus than in the cortex. On the contrary, the cortex CBF was mostly preserved or even elevated in both groups of patients. We speculate that CBF reduction in patients with a chronic subdural hematoma occurs initially in central cerebral areas like the basal ganglia and thalamus, and then extends to the entire hemisphere including the cortex as brain compression and displacement progress. Central cerebral area involvement might be more responsible for clinical symptoms than the cortex. 