The study investigated the relationship between genetic variants of the CYP2C19 enzyme and the risk of coronary atherosclerosis in patients with type 2 diabetes mellitus. 4,627 patients with diabetes were included in the research - 2,390 with complications of coronary atherosclerosis and 2,237 with diabetes only. Patients were divided according to their CYP2C19 metabolic type into rapid, intermediate and poor metabolizers. The results showed that patients with intermediate and poor metabolism of CYP2C19 had a higher frequency of coronary atherosclerosis compared with rapid metabolizers. Logistic regression analysis confirmed that the CYP2C19 intermediate and poor metabolizer phenotype was independently associated with a higher risk of coronary atherosclerosis (odds ratio: 1.290). In addition to genetic factors, other factors were associated with the development of atherosclerosis: advanced age, overweight, smoking, alcoholism, hypertension, and dyslipidemia, with dyslipidemia being significantly higher in patients with atherosclerosis (41.1% versus 18.8%). The study suggests that genetic testing of CYP2C19 could help identify diabetic patients at higher risk of coronary atherosclerosis.