The objective of the study was to investigate the effect of enteral immunonutrition and standard nutrition on the changes of selected cellular immune parameters during the early post-operative period in patients after with pancreatic cancer surgery. Prospective, randomized studies performed in 41 patients after pancreaticoduodenectomy receiving early enteral standard nutrition (group I, n=22) or enteral immunonutrition (group II, n=19). The dynamics of changes for the following cell percentage: CD3+, CD4+, CD4+/CD25+, CD4+/CD38+, CD8+, CD8+/CD38+, CD8+/CD25+, CD19+, CD19+/CD95+, CD19+/CD38+, CD19+/CD34+, CD14+, CD14+/HLADR+, CD14+/CD68+, was evaluated before and on post-operative day 1, 3, 7 and 10 using flow cytometry. A significant improvement in cellular immune response was most frequently noted in the group of patients treated with early enteral immunonutrition. In comparison with pre-operative values for group II, a significant increase in the subpopulation of lymphocytes CD4+ (p=0.02), CD4+/CD25+ (p=0.02), CD4+/CD38+ (p=0.006) was observed on day 7 and 10. In patients receiving immunonutrition between days 3 - 10 after operation, the percentage of CD19+ cells was significantly higher (group I vs. group II, respectively: 5.38±4%; 17.53±14% p=0.001, 5.75±4%; 10.52±5% p=0.01 and 5.12±3%; 17.34±4.8 p=0.001). In patients receiving standard enteral nutrition no significant changes in the subpopulation of CD4+, CD4+/CD25+, CD4+/CD38+ and CD8+ lymphocytes were noted. The percentage of remaining lymphocyte subpopulations (CD3+, CD8+/CD38+, CD19+/CD95+) in both groups did not significantly change. The early enteral immunonutrition as compared with standard enteral nutrition shows an immunomodulative effect on the changes of cellular immune response after pancreatoduodenectomy. Among the evaluated immune parameters only the change of dynamics in percentage of lymphocyte B (CD19+ cells) in patients with no complications after pancreatic cancer resection is an early marker for cellular response to enteral immunonutrition.