OBJECTIVE The magnitude of the blood oxygen dependent level (BOLD) functional MRI (fMRI) response to visual stimulation is reduced in the small vessel disease cerebral amyloid angiopathy (CAA), reflecting impaired vascular reactivity. We determined whether BOLD responses were reduced in another small vessel disease, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). METHODS BOLD fMRI data were collected using a visual stimulus (contrast-reversing checkerboard) and motor task (finger-tapping). The amplitude of BOLD responses in the visual cortex (visual stimulus) and motor cortex (motor task) were compared between 5 CADASIL, 18 CAA and 18 control subjects, controlling for age and hypertension. RESULTS BOLD response varied by group for the visual stimulus (p<0.001) but not the motor task (p=0.47). After adjusting for age and hypertension, the estimated mean visual cortex BOLD amplitude response was 3.95% in CADASIL (95% confidence interval, CI 3.15-4.75%), 1.73% in CAA (95% CI 1.19-2.27%), and 2.88% (95% CI 2.39-3.37%) in controls. In CADASIL, the visual BOLD response was greater than in CAA (p<0.001) and controls (p=0.04). CONCLUSIONS We observed increased and unchanged BOLD amplitude responses in the visual and motor cortices of CADASIL patients, respectively. This suggests that cortical blood flow regulation by neuronal activity may be relatively preserved in CADASIL, in contrast to CAA where occipital vascular reactivity is impaired. Cortical vascular reactivity in CADASIL may be preserved because the disease-related injury is primarily subcortical, whereas increased activation may reflect compensatory mechanisms for subcortical injury.