Vascular dementia (VaD) is a term used to describe a particular constellation of cognitive and functional impairment, and is now generally seen as a subset of the larger syndrome of vascular cognitive impairment (VCI). The latter is seen as cognitive impairment in the face of cerebrovascular disease. VCI can be classified clinically by whether patients meet criteria for dementia, and whether the syndrome is distinct or overlaps with primary neurodegenerative diseases, such as Alzheimer's disease. This clinical classification can be further classified by neuroimaging, with subgroups that show cortical infarction, subcortical infarction and white matter changes, each alone or in combination. Understood in this way, VCI is likely the most common form of cognitive impairment in the population. Attempts to treat VaD had varying degrees of success, but it now appears that many forms of VCI might be preventable, especially with good control of vascular risk factors in middle age.