Background. Vasopressin, in cooperative interaction with angiotensin II, participates in cardiovascular regulation and it increases in arterial hypertension. In addition, vasopressin is involved in tumorigenesis through angiogenesis by stimulating protein synthesis in endothelial cells, induction of endothelin-1, influencing cell proliferation, and stimulating growth factors through VIA receptors in the kidneys. To assess the content of vasopressin, a measurement of copeptin, its precursor, produced in an equimolar ratio, is used.Objective: to determine the content of serum copeptin and to reveal correlations with the indices of the renin-angiotensin system in the tumor and blood serum in patients with localized kidney cancer (КС) with arterial hypertension (AH).Materials and methods. The inclusion criteria for the study were initially diagnosed localized KC T1N0M0 without special treatment, age less than 75 years, essential AH of I—II degree without treatment, controlled by angiotensin-converting enzyme inhibitors (ACEi). All patients were divided into groups: patients with KC (n = 42); KC + AH without treatment (n = 31); KC + AH + ACEi (n = 32). Serum levels of copeptin and angiotensin I, II, 1-7 and angiotensin-converting enzyme, angiotensin-converting enzyme 2 were determined by ELISA. Also, the level of components of the renin-angiotensin system was assessed in tumor tissue samples obtained by robotic-assisted kidney resection.Results and conclusion. In patients of the KC + AH group, the median of the indicator is statistically significantly higher than in the group of healthy donors (2.4 times at p <0.05). In the group KC + AH + ACEi, a decrease in the content of the studied indicator was found in comparison with the norm by 1.2 times (at p <0.05). It was found that the content of copeptin in the tumor less than 4 cm in comparison with the size of 4-7 cm is significantly lower (KC p = 0.045, KC + AH p = 0.067 and KC + AH + ACEi p = 0.036). Correlation analysis showed direct significant links between high density between the levels of copeptin and angiotensin II in the tumor and blood, and moderate tightness with tumor and serum levels of angiotensin (1-7). Multiple regression analysis revealed that the most significant factors that have a positive effect on the concentration of serum copeptin are the content of angiotensin II in the tumor and blood serum, the tumor concentration of angiotensin (1-7) and angiotensin-converting enzyme 2, as well as the level of systolic blood pressure (p <0.05).