The aim of this study was to evaluate the impact of standard parenteral and immunomodulating nutrition on clinical status, a number of complications, time of hospitalization in patients operated because of the gastric cancer. The patients nutritional status before and after surgery was determined as well as a correlation between malnutrition and immune reaction monitored via IL-6, IL-10, IL-12, IL-18, TNF-α. The randomized study took place in the Department of General Surgery UJCM in Cracow. In the first test group were 45 participants receiving immunomodulating diet, the control group consisted of 54 patients selected for standard parenteral nutrition. The level of cytokines was measured in serum and peripheral blood mononuclear cells cultures after stimulation with PHA and LPS before the surgery and in the 1st, 2nd and 7th day after surgery. In about 30% of participants malnutrition was determined and in was intensified after surgical trauma. The change of cytokines dependent on nutritional status before surgery was observed. In the group of patients receiving immunomodulating diet, especially those with malnutrition before surgery, smaller total number of complications was observed in postoperative term. The high concentration of IL-6 before surgery and in the 1st and 3rd day after surgery as well as the high concentration of IL-10 in 3rd and 7th day has the influence on complications development. Measuring concentrations of cytokines in patients after serious surgery allows detecting response disorders of the immune system to operational trauma. Immunomodulating diet applied in the postoperative period results with objective clinical and economical benefits in patients qualified to the malnourished group.