This chapter reviews current literature of CVR in the context of aging, cognitive impairment, and dementia. CVR decreases with age in a spatiotemporally specific manner, with longitudinal studies revealing more rapid rate of decline compared to cross-sectional investigations. CVR is further reduced in cognitive impairment and dementia, the mechanism of which is independent of Alzheimer’s pathology. Diminishment of CVR was related to classic vascular hallmarks such as white matter hyperintensities, but with a larger spatial scope. The reduction of CVR was also found to have a negative impact on cognitive function. CVR appears to be a modifiable marker which may be useful in detecting the effect of treatment/intervention on brain vascular function. CVR may also play an important role in the interpretation of fMRI data in aging and dementia by separating vascular from neural contributions in activation signal. Existing evidences suggest that CVR may be a promising biomarker in understanding brain aging and in the diagnosis and treatment monitoring of neurodegenerative diseases.