Subcortical ischemic vascular dementia (SIVD) has been proposed as a subtype of vascular cognitive impairment. MRI often discloses “silent” hyperintensities in 20% to 40% of community-dwelling elderly. Efforts to relate MRI-measured lacunes and white matter changes to cognitive impairment have not been straightforward. The possibility that Alzheimer’s disease pathology contributes to cognitive impairment increases with age. A rare disorder known as cerebral autosomal dominant arteriopathy with subcortical infarctions and leukoencephalopathy (CADASIL) provides an opportunity to study SIVD in the absence of Alzheimer’s disease. Lacunes and deep white matter changes are associated with dysexecutive syndrome. Hypertension, the leading risk factor for sporadic SIVD, is treatable. High priority must be given to reducing vascular risk profiles.