Objective: Our aims were to evaluate the plasma vitamin A status and the function of T-cell dependent immunity in lung cancer patients， so as to explore the correlation between them. Methods：We measured the plasma vitamin A status with HPLC and checked the subsets of T lymphocyte with indirect immunofluorescence technique. Results： The levels of plasma vitamin A in lung cancer patients and in controls were(0.406±0.111)mg/L and(0.548±0.149)mg/L respectively . There was a significant difference between them(P＜0.001) . The levels of CD3， CD4，and CD4/CD8 were lower in lung cancer patients than those in controls， while the level of CD8 was higher. The plasma vitamin A had positive correlation with CD3 , CD4，and negative with CD8. Conclusion： There is defect of the plasma vitamin A and low level of the function of T cell dependent immunity in lung cancer patients，which shows the obvious correlation between them. This research supplies the basis of clinical therapy to lung cancer with vitamin A.