At the moment, there are a large number of studies devoted to the influence of various aspects of coronary bypass surgery on the formation of POCD, however, there is still no clear understanding of the mechanisms of this effect. Despite the fact that as a result of many studies a qualitative assessment of the predictors of POCD has been given, there is still no quantitative assessment of these factors. The aim of the study was to study the effect of the duration of CABG surgery on the formation of postoperative cognitive dysfunction in elderly patients. Materials and methods. The study involved 60 elderly and middle-aged patients suffering from ischemic heart disease, stenosing coronary sclerosis, functional class III-IV angina pectoris, who underwent coronary bypass grafting under cardiopulmonary bypass and pharmaco-cold blood cardioplegia, who are being treated at the cardiac surgery department of the Belgorod Regional Clinical Hospital of St. . Belgorod), from 2019 to 2021. The duration of the operation and cognitive status were assessed using the MMSE method. Results. It was determined that the negative dynamics of MMSE in elderly patients is observed with the duration of the operation by 7.5[20.6-12.3]% less than in the middle age group. And the positive dynamics of MMSE in the elderly group was detected during the operating period by 12.56 [15.0–4.29]% less than in the middle age group. From which it follows that a long operating period has a greater negative effect on elderly patients than on middle-aged patients. Conclusions. In elderly patients, a negative dynamics of cognitive status is noted with a shorter operation time than in middle-aged patients, which suggests that elderly patients are more sensitive to the negative impact of the operation duration than middle-aged patients.