Arterial hypertension, cerebrovascular disease, and dementia are related pathologies. This paper has reviewed comparatively the incidence of arterial hypertension and adult-onset dementia disorders. Hypertension is associated with cerebrovascular disease, which is in turn associated with dementia. It is the most important modifiable risk factor for stroke, which is a recognized cause of vascular dementia. In terms of pathophysiology of hypertensive brain damage, several hypotheses were developed, such as that vascular alterations induced by hypertension can induce lacunar or cortical infarcts and leucoaraiosis, that hypertension is responsible for cerebrovascular disease and acts into the contest of a pre-existing subclinic Alzheimer's disease (AD), that hypertension determines neurobiologic alterations (such as beta-amyloid accumulation) resulting in neuropathologic damage, and that aging and cerebrovascular risk factors act together to cause cerebral capillary degeneration, mitochondrial disruption, reduced glucose oxidation, and reduced ATP synthesis. The consequence of these alterations are neuronal death and dementia. Macroscopic results of these mechanisms are the so-called white matter lesions (WML), the significance of which is analyzed. Increasing clinical evidence suggests a close relationship between the reduction of elevated blood pressure and countering of both vascular dementia and AD. Antihypertensive treatment probably influences cognitive performances and prevents cognitive function alterations and the development of dementia. It is therefore important to evaluate as soon as possible cognitive functions of hypertensive patients.