Aim. To determine the features of coronary lesions in patients with chronic coronary heart disease (CHD) and type 2 diabetes mellitus (DM), to analyze their relationship with polymorphic variants of the paraoxonase gene (PON) 1. Design. A cross-sectional retrospective observational study. Materials and methods. The study included 200 patients with a stable form of IHD, divided into two groups: the main group included 112 people with IHD in combination with type 2 diabetes, the comparison group included 88 patients without carbohydrate metabolism disorders. All patients underwent selective coronary angiography (CAG) using a General Electric INNOVA 3100IQ angiographic unit (GE, USA) according to the M. Judkins method. Real-time polymerase chain reaction (PCR) was used to determine the rs622 polymorphism of the PON1 gene. Statistical processing of the obtained results was carried out using the IBM SPSS Statistics Version 25.0 software package (International Business Machines Corporation, USA). Results. In patients with coronary artery disease on the background of type 2 diabetes, coronary lesions were more often of a multivessel nature (p = 0.015) with the development of hemodynamically significant stenoses (p = 0.027); compared with patients with coronary artery disease without diabetes, they had more cases of lesions in the middle and distal parts of the arteries (p = 0.005 and p = 0.038, respectively). Multivascular coronary disease in patients was associated with the presence of the GG genotype rs622 of the PON1 gene (in the main group p = 0.010, odds ratio (OR) = 5.098, confidence interval (95% CI) — 1.337–19.433, in the comparison group p = 0, 02, OR = 7.143, 95% CI — 1.287–39.630). The AG genotype of the rs622 polymorphism of the PON1 gene has a protective effect against widespread lesions of the coronary arteries in patients with coronary artery disease and type 2 diabetes (p = 0.019, OR = 0.377, 95% CI — 0.165–0.860) and the development of hemodynamically significant stenoses of the coronary arteries in patients with IHD without diabetes (p = 0.005, OR = 0.255, 95% CI — 0.966–0.676). Conclusion. In patients with coronary heart disease and type 2 diabetes, coronary angiography demonstrated pronounced atherosclerotic changes in the coronary arteries. Multivessel coronary lesion is associated with the GG genotype of the rs622 polymorphism of the PON1 gene, which determines the possibility of predicting and further preventing the development of coronary heart. Key words: coronary heart disease, coronary atherosclerosis, type 2 diabetes mellitus, multivessel lesion, gene polymorphism, paraoxanase 1