The aim of the study was: the evaluation of usefulness of BNP and cTnI measurement for diagnosing PMI, the evaluation of changes in fT3, fT4 and TSH levels, the assessment of diagnostic value of these changes before and after CABG. Studied groups: group I, the patients without PMI, group II, the patients with PMI after surgery, group III, the patients without cardiovascular disturbances (IIIa, the patients in euthyroid state, IIIb, the hyperthyroid patients). In group I, II the cTnI and BNP levels were measured before surgery and 8, 12, 16, 24, 48, 72 hours after CABG. The plasma fT3, fT4 and TSH concentrations were measured before surgery and 8, 16, 24, 72 hours after CABG. In group III plasma fT3, fT4, TSH, BNP and cTnI concentrations were measured once. The mean levels of fT4 and fT3 were similar in group I and II at any point of time. Before surgery the mean TSH value in group II was higher than in group I (p<0.03). The mean BNP level in group I was lower than in group II before surgery (p<0.05) and at each time point after surgery (p<0.01-p<0.001 respectively). Before CABG the mean cTnI value was similar in group I and II. After surgery the mean cTnI levels was significantly higher in group II than the mean value in group I (p<0.001). Conclusion: The cardiac troponin I level should be measured for the confirmation of PMI. The evaluation of the changes of BNP concentration in perioperative time can have only supportive value in diagnosting of PMI. The measurement of TSH concentration before surgery can be used as an additional, prognostic marker of PMI in patients undergoing CABG.