Abstract Chronic subdural hematoma is a frequent disorder in the elderly. Although intensively investigated, numerous aspects, including the pathophysiology of clinical symptoms, remain unclear. Perfusion deficits are likely to induce the transient neurologic symptoms seen in chronic subdural hematoma (cSDH). The aim of the present study was to quantify cerebral perfusion impairment in cSDH. Before surgery, 34 patients were examined neurologically using the National Institutes of Health Stroke Scale (NIHSS) score and investigated by CT perfusion imaging. Hematoma volume, localization, and hematoma configuration were recorded. Clinical and radiological data were correlated. Mean hematoma volume was 91.8 cm(3) (16.2-241.6 cm(3), standard deviation [SD] 49.5). Whole brain mean transit time (MTT) was slightly elevated (mean 36.6 sec, SD 5.8). Hematoma volume and cerebral blood volume (CBV) in the underlying hemisphere correlated marginally but not significantly (p=0.067). Perfusion parameters determined in the area below the hematoma (ABH) and the corresponding contralateral cortex (MAC) were highly significantly different regarding cerebral blood flow (CBF) (mean 88.8 vs. 70.4, p<0.01) and CBV (mean 29.4 vs. 22.5, p<0.01). On the other hand, MTT and Tmax were almost equal between these areas (MTT means 35.0 vs. 34.8, (p)=0.914; tMax means 16.0 vs. 15.4, p=0.587). We conclude that local brain perfusion autoregulation is active in the cortical area below cSDH. CBV and CBF are significantly upregulated in the cortical area below cSDH indicating the effect of autoregulation in tissue at risk of ischemia. Cerebral autoregulation is intact in cSDH. Neurologic deficits are likely induced by borderline perfusion.