The aim of the study was to evaluate the protective effects of nitric oxide on platelets. The study included fifteen patients divided into two random groups. In the test group nitric oxide was added to the oxygenator at a concentration of 10 ppm. The control group was subjected to the standard procedure. In all patients, blood was sampled at three time points: before surgery, immediately after surgery, and at least 24 hours after cardiac surgery. The following tests were performed: ASPI test, ADP test, morphology, indication of platelet monocyte aggregates VASP-P, CD41a, CD42a, CD61 by flow cytometry. There were no statistically significant differences between groups.