Insomnia is frequently detected in patients with arterial hypertension (AH): from 19% to 47.9% of all cases according to epidemiological studies. On the other hand, the frequency of hypertension in patients with insomnia ranges from 21.4% to 50.2%, whereas in patients without insomnia, from 11.0% to 41.8%. In single studies in which patients with insomnia underwent ambulatory blood pressure monitoring (ABPM), these patients showed higher nocturnal blood pressure levels. Recent data suggests that insomnia is also a risk factor for hypertension. Among the pathogenetic mechanisms explaining the relationship between hypertension and insomnia, an increase in the activity of the main neuroendocrine stress systems, sympatho - adrenal and hypothalamic - pituitary - adrenal, and the frequent presence of concomitant anxiety disorders are discussed. To determine the sleep quality in patients with insomnia, the Pittsburgh Sleep Quality Index (PSQI) is most often used, patients with hypertension in a number of studies had higher total PSQI score compared to individuals with normal blood pressure. PSQI score correlates with systolic and diastolic blood pressure level, as well as with the presence of non - dipper blood pressure profile. Both hypertension and insomnia are associated with impaired cognitive functions. However, the relationship between cognitive impairment and insomnia is rather contradictory, which is most associated with the methodology for assessing cognitive functions and differences in the initial clinical and demographic characteristics of the examined patient population.