Background. Platelets play a key role in the pathogenesis of acute coronary syndrome (ACS). In recent years, the amount of data on the advisability of using the platelet function test (PFT) in the appointment of antithrombotic therapy has been growing.Objective. To access PFT in patients with unstable angina and various comorbidities.Design and methods. The study involved 74 patients with the diagnosis of unstable angina. All patients underwent standard clinical examination, PFT (impedance aggregometry with ADP and collagen), assessment of Charlson comorbidity index.Results. The most frequent comorbidities were: hypertension (95 %), type 2 diabetes mellitus (30 %), excessive body weight (35 %), multifocal atherosclerosis (22 %), smoking (24 %). Half of the patients (n = 36) had high level of comorbidity. Patients with a comorbidity index of 5 or more had high platelet aggregation on the 3rd day of hospitalization. Elderly patients, smokers, as well as patients with diabetes mellitus type 2 and multifocal atherosclerosis also had higher values of platelet activity, which may be associated with unfavorable prognosis and risk of recurrent events.Conclusion. We revealed association between PFT and comorbidities both with risk factors or diseases alone and in its integral assessment using the Charlson comorbidity index. Among the individual risk factors, smoking, diabetes mellitus and multifocal atherosclerosis were the most important, which confirms their direct role in the pathogenesis of thrombotic complications.