The aim of the study was to calculate the amount of surgical injury caused by systematic lymphadenectomy of mediastinum in patients operated on due to non-small cell lung cancer, with uneventful postoperative course. The study group consisted of 11 patients with cancer of the fight lung (Group 1). The control group consisted of 12 patients with left lung cancer (Group 2). In patients with right lung cancer systematic lymphadenectomy, while in patients with left lung cancer systematic sampling was performed. Serum IL-6 and IL-1ra concentration was measured before and after surgery, and on postoperative day 1,3, and 7, as well as in sputum at the end of surgery and in pleural fluid on postoperative day 1, by ELISA test. Peripheral blood lymphocyte (PBL) count was measured with flow cytometry. Time of surgery was higher in patients with fight than left lung cancer [(154.1±31.29) vs (119.6±24.81) rain; P=O.O08)]. The number of resected mediastinal lymph nodes was higher in patients with right than left lung cancer [(27.6±7.6) vs (11.18.1); P-0.O0006)]. Postoperative decrease of PBL was significantly higher in group 1 than 2 [(1.25±0.37) vs (1.75±0.64)×103/μL; P=0.04)]. No significant differences were found in serum, pleural fluid and sputum concentration of IL-6 and IL-1ra between groups. Negative correlation between concentration of these cytokines in pleural fluid and number of reseeted mediastinal lymph nodes was found (Spearman test for IL-6: r=-0.723; P<0.001; for IL-1ra: r=-0.768; P<0.001). Number of positive N2 lymph nodes did not correlate with pleural fluid concentration of eytokines. Systematic lymphadanectomy of the mediastinum causes immunosuppression, as measured by decreased count of PBL and a negative correlation between number of resected mediastinal lymph nodes and concentration of cytokines in pleural fluid.