We studied the changes of electroencephalograms (EEG) related to on-pump coronary artery bypass grafting (CABG) in 28 right-handed male patients with coronary heart disease (CHD), 10 from which had accompanying moderated (30-50%) carotid artery (CA) stenoses. All EEG studies were performed 3-5 days before and 7-11 days after CABG. EEG data of healthy age-matched males (n=14) were examined. Before surgery, the CHD patients differed from the control group by less expressed theta2 and beta1 rhythm power asymmetry. The differences demonstrated worse conditions for cognitive processes in CHD patients. After CABG, the higher power of teta1 and 2 rhythms, predominantly in the frontal lobe of the left hemisphere which was mostly expressed in patients with CA stenosis, was observed in all CHD patients. This effect can be considered as the appearance of ischemic neuronal injury caused by on-pump CABG. The localization of changes in the frontal cortex of the left hemisphere can be related to a high vulnerability of these regions. The deficit of cerebral blood flow in these regions will define a clinical picture of cognitive decline after CABG.