Background and Purpose— Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a progressive systemic nonatherosclerotic angiopathy which causes ischemic strokes and vascular subcortical dementia. A cross-sectional study was performed to examine the retinal vascular caliber and blood flow in CADASIL. Methods— Scanning laser Doppler flowmetry was used in a case–control study (11 patients and controls) of peripapillary retinal circulation. Automated full-field perfusion image analysis was used to analyze the flow data. Retinal vessel calibers were measured from retinal images acquired with scanning laser ophthalmoscopy. The caliber of the superior and inferior temporal retinal artery and vein were measured 1 and 2 mm from the disc rim, and the mean values were used for analysis. Results— Retinal capillary peak systolic flow (mean, 249 versus 311 arbitrary unit [AU]; P =0.072) was lower, and mean capillary flow (mean, 184 versus 224 AU; P =0.12) and minimum diastolic flow (mean, 105 versus 132 AU; P =0.16) tended to be lower in patients than in controls. No significant difference in the calibers of proximal retinal arteries (mean, 104 versus108 μm) and veins (mean, 150 versus 145 μm) was found between the patients and controls. Conclusions— Retinal capillary blood flow is mild to moderately reduced in CADASIL but that does not appear to cause major ischemic injury. Such reduction is analogous to that in the cerebral cortex in CADASIL patients with which retina appears to share its relative sparing from severe arterial ischemic tissue damage.