Abstract Background Poor adherence to pharmacological treatment among patients with hypertension (HTN) is common. Approximately half of HTN patients do not use their medications as prescribed. Multiple barriers can influence adherence to antihypertensive medications. HTN patients may be characterized by the presence of frailty syndrome (FS) and cognitive impairment (CI). FS and CI may adversely affect the course of the disease and adherence to therapeutic recommendations. Purpose To assess the adherence and its determinants among patients with hypertension. Methods The study included 129 patients diagnosed with hypertension (81 men, 48 women; mean age M±SD=69.98±11.67) hospitalized in the Department of Occupational Diseases and Hypertension. Medical record analysis, the author's sociodemographic questionnaire, the Tilburg Frailty Idicator (TFI) to determine the presence of frailty syndrome, the Montreal Cognitive Assesment (MoCa) questionnaire to assess cognitive function, and the Adherence to Medication Scale (ARMS) to assess adherence were used. Results The majority of respondents were male (62.79%), living in large cities (31.78%), in a relationship (61.24%), with a high school education (68.22%), and retired (67.44%). Analysis of medical records among comorbidities showed diabetes (59.69%) and other cardiovascular diseases (58.91%) to be the most common. Hospitalizations due to hypertension within the past year in the range of 1-2 were reported in 72.09% of the subjects, 3-5 hospitalizations in 17.05%, and more than 5 hospitalizations in 10.85% subjects. The surveyed patients mostly kept self-monitoring diaries (61.24%), measured their blood pressure values 2-3 times a day (58.15%) with an upper arm blood pressure monitor (64.34%). In terms of self-care behaviors, respondents most often indicated following a diet with a restriction of unhealthy fats (52.71%), following a low-sodium diet (44.19%) and being physically active (33.33%). The mean blood pressure values in the study group were M±SD=139.73±16.73 mmHg for SBP and M±SD=81.48±13.25 mmHg for DBP, respectively. On the basis of the TFI, 99.22% of patients showed the presence of FS (M±SD =10.66±2.82), the MoCa questionnaire indicated abnormal values in cognitive function in 79.07% (M±SD =18.16±8.3). The average adherence ARMS score was M±SD 17,6±6,72 pcts. (higher the ARMS score the worse adherence). Univariate analysis as determinants of adherence showed unemployment (b=9.391;p=0.001), smoking (b=6.701;p=0.001), duration of illness (b=-0.153;p=0.003), 3-5 hospitalizations in the past year (b=3.891;p=0.014). Multivariate analysis among determinants of adherence showed unemployment (b=7.556;p=0.022), duration of illness (b=-0.167;p=0.002) and 3-5 hospitalizations (b=5.011;p=0.001). Conclusion Hypertensive patients are characterized by optimal adherence. Despite expectations, cognitive impairment and frailty syndrome did not determine adherence to medications.