Objective:To investigate the change of the expression of CD28 on T-lymphocyts of the peripheral blood in the elderly patients with lung cancer. Methods:Three-color fluorescent flow cytometry were used to analyze the percentage of peripheral blood T-lymphocyts and T cell subsets in both of 35 normal elderly persons and 32 elderly patients with lung cancer. Results:CD3+-CD4+-CD8+-CD4+CD28+-CD8+CD28+T cells in the peripheral blood of the elderly patients with lung cancer were significantly lower than those in the normal elderly persons(P < 0.01);CD8+CD28-(P < 0.01) T cells in the peripheral blood of the elderly patients with lung cancer were significantly higher than those in the normal elderly persons.However there was no significant difference between two groups of CD4+CD28- T cells. Conclusion:Elderly group patients with lung cancer had a significantly lower cellular immunity dysfunction and anticancer ability than those in normal elderly persons,which led to their illness worse.