Mutations in NOTCH3 are the cause of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) an inherited small vessel disease leading to subcortical strokes and dementia. Since the vascular pathology is clearly defined, CADASIL may provide important insights into the mechanisms underlying lacunar infarcts, ischemic white matter changes, and vascular dementia. Evidence from different sources suggests a central role for vascular smooth muscle cells (VSMC) in the pathophysiology of the disease. This article gives a brief overview on the phenotypic spectrum of the disease and discusses some of the relevant disease mechanisms that lead from Notch3 mutations to ischemic infarcts.