The purpose of the study was to determine the features of thrombosis (D-dimer) and inflammation (procalcitonin) in patients with COVID-19 with acute respiratory syndrome in combination with essential hypertension and to determine their role as markers of severity and prognosis of comorbid pathology. Materials and methods. A retrospective study of the medical records of 232 patients with confirmed COVID-19 disease with acute respiratory syndrome was performed. Patients were divided into two groups: with comorbid essential hypertension (main group) and without essential hypertension (comparison group), which amounted to 149 and 83 persons, respectively. The information obtained from the medical records included demographic data, symptoms and course of the disease, complications, instrumental and laboratory results (including peripheral blood platelet count, international normalized ratio, D-dimer and procalcitonin levels), and data of patients’ treatment. Results. According to the results of the study, the number of patients hospitalized in the intensive care unit with respiratory viral disease COVID-19 and comorbid hypertension, both in absolute and relative terms, was significantly higher (p = 0.005). The number of patients in this group who required non-invasive lung ventilation was also significantly higher (39% versus 17%), indicating a more severe and rapid course of the disease. In terms of hospitalization, both groups of patients had no significant differences, but the mortality rate in the group with comorbid essential hypertension was significantly higher (p = 0.005). In our study, level of D-dimer in patients of both study groups exceeded the reference values, but it was significantly higher in patients of the main group, compared with patients in the comparison group (p = 0.005). According to the platelet counts and international normalized ratio in patients of both groups no significant differences were found (p = 0.10 and p = 0.32, respectively), there was only a slight increase in peripheral blood leukocytes at the time of hospitalization in patients of the main group (p = 0.083). In addition, in patients with combined pathology, the mortality rate was higher and, at the same time, it was in these patients that direct correlations of strong density were found between D-dimer and procalcitonin with mortality (r = 0.77, and r = 0.72, respectively, p = 0.001 and p = 0.003). Conclusion. In patients with COVID-19 with acute respiratory syndrome, there is a significant increase in markers of thrombosis (D-dimer) and inflammatory activity (procalcitonin), while the severity of their changes is significantly greater in patients with comorbid essential hypertension. Patients with COVID-19 with acute respiratory syndrome in combination with essential hypertension have a more severe course of the disease and a significantly higher mortality rate, which is associated with a tendency to develop thrombocytopenia and is associated with changes in markers of thrombosis and inflammation. Determination of D-dimer and procalcitonin levels are reliable markers for both severity and prognosis in patients with COVID-19 with severe acute respiratory syndrome, and especially in conditions of comorbidity with essential hypertension, which may have a significant impact on strategy selection and tactics of treatment of such patients