Background. Omentin-1 (QM-1) — one of the most important anti-inflammatory adipocytokines produced by adipose tissue. It is known that its concentration is reduced in obese patients. However, the role of OM-\ in the pathogenesis of coronary heart disease (CHD), including acute coronary syndrome (ACS), is not fully determined.The objective of the study — to assess the level of OM-1 in blood serum of patients with ACS without ST-segment elevation (ACSWEST) who underwent percutaneous coronary intervention (PCI) and patients with stable CHD.Design and methods. Examined 104 patients with ACSWEST undergoing PCI. Comparison groups consisted of 38 patients without CHD according negative results of stress-echocardiography or coronary angiography, as well as 80 patients with stable CHD. All patients were evaluated anthropometric indicators: height, weight, waist circumference (WC), body mass index (BMI). Serum concentrations of OM-I were determined by enzyme immunoassay (DRG,USA), serum lipid profile was determined by enzymatic method.Results. In patients with ACSWEST who underwent PCI, the concentration of OM-I in the blood is lower than in those examined without atherosclerotic lesions of the coronary arteries [7.53 (5.00-10.55) ng/ml and 12.56 (7.84-15.34) ng/ml, respectively; p < 0.001). The concentration of OM-1 in the blood in patients with ACSWEST and a stable CHD did not differ (p > 0.05). In patients with ACSWEST, the concentration of OM-1 blood with multivascular lesions of the coronary arteries is lower than with 1-2 vascular lesions [7.30 (3.91- 8.17) ng/ml and 9.44 (6.54-9.93) ng/ml, respectively; p < 0.001. Similar patterns were established in patients with a stable CHD (p < 0.001).The concentration of OM-1 inthe blood in women with ACSWEST, with stable CHD and in those examined without CHD was higher than in men of the corresponding groups (p < 0.001).In patients with ACSWEST and with a stable CHD with overweight and obesity (WHO, 1999), the concentration of OM-1 inblood serum is lower than in patients with CHD and normal BMI (p < 0.001). In patients with ACSWEST and AO, the level of OM-1 inthe blood is lower than in patients with ACSWEST without AO, both in men and women (p < 0.001). When conducting a regression analysis, it was found that the concentration of OM-1 inthe blood of patients with ACSWEST is determined by BMI (b = -0.30, beta = -0.23, p = 0.002) and patient gender (b = 2.21, beta = 0.16, p = 0.029); in patients with a stable CHD — BMI (b = -0.38, beta = -0.27, p = 0.029).Conclusion. For patients with CHD, both with ACSWEST and with stable CHD, a low level of OM-1 in the blood is characteristic. The lowest OM-1 values were found in patients with multivascular coronary artery disease and obesity. The gender characteristics of the concentration of OM-1 in serum were established: the concentration of OM-1 in serum in women is higher than in men. A decrease in the concentration of OM-1 in the blood in patients with ACSWEST and with stable CHD is associated with BMI, the patient’s gender, and the severity of coronary atherosclerosis.