Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a single-gene disease of the cerebral small blood vessels caused by mutations in the NOTCH3 gene on chromosome 19. Although CADASIL was known as a rare disease, recent research has suggested that the NOTCH variants could be found frequently even in the general population. The main clinical features included recurrent stroke, migraine, psychiatric symptoms, and progressive cognitive decline. On brain magnetic resonance imaging, patients with CADASIL showed multifocal white matter hyperintensity lesions, lacunar infarcts, microbleeds, and brain atrophy. Among them, lacunar infarcts and brain atrophy are important in predicting the clinical outcomes of patients with CADASIL. In the Jeju National University Hospital, we have diagnosed 213 CADASIL patients from 2004 to 2020. Most NOTCH3 mutations were located in exon 11 (94.4%), and p.Arg544Cys was the most common mutation. The mean age at diagnosis was 61.0±12.8 years. The most common presenting symptoms were ischemic stroke (24.4%), followed by cognitive impairment(15.0%), headache (8.9%), and dizziness(8.0%). Although the exact prevalence of CADASIL in Jeju is still unknown, the disease prevalence could be as high as 1% of the population considering the prevalence reported in Taiwan. Therefore, it is necessary to discover efficient biomarkers and genetic tests that can accurately screen and diagnose patients suspected of having CADASIL in this region. Ultimately, it is urgent to explore the exact pathogenesis of the disease to identify leading substances of treatment potential, and for this, multi-disciplinary research through active support from the Jeju provincial government as well as the national government is essential.