Abstract: Objective 　To investgate the effect on immune function of patient s with non2small cell lung cancer (NSCLC) t reated with gemcitabine and cisplatin regimen. Methods 　The prevalence of CD4 +CD25 + Foxp3 + T regulatory ( Treg) cells in peripheral blood in 38 patient s with NSCLC, t reated with gemcitabine plus cisplatin chemotherapy regimen, was detected by flow cytomet ry. Results 　The percent2 age of CD4 + CD25 + Foxp3 + Treg cells in peripheral blood of the patient s with NSCLC pre2chemotherapy was significantly higher than that in healthy doners ;compared with pre2chemotherapy, the percentage of CD4 + CD25 + Foxp3 + Treg cells in peripheral blood was significantly decreased in post2chemotherapy pa2 tient s ( P < 0. 05) ; there were no significant differences observed among squamous cell carcinoma, adeno2 carcinoma and adenosquamocarcinoma ( P > 0. 05) . Conclusion 　Gemcitabine plus cisplatin chemotherapy can improve the immune2tolerance in advanced non2small cell lung cancer patient s.