We report 3 cases of Cadasil with dementia. In the 3 cases, the dementia had a subcortical and frontal presentation. It associated behavioural symptoms, amnesia, executive functions disturbances, bradyphrenia, slowing of information processing and frontal symptoms, without aphasia, apraxia or agnosia. One patient showed overt dementia before any focal neurological sign. Imaging of the brain was consistent with subcortical infarcts and leukoencephalopathy, without involvement of the cerebral cortex. We suggest that dementia and psychoaffective disturbances are major diagnostic criteria for Cadasil. This pathology is probably a good model for the neuropsychological study and the physiopathological analysis of the concept of subcortical dementia.