Objective:To explore the value of 18F-FDG PET/CT on clinical staging and assessment of chemotherapy response in patients with diffuse large B-cell lymphoma(DLBCL). Methods:18F-FDG PET/CT was performed before and after 3 or 4 cycles of chemotherapy in 29 patients with DLBCL. The patients were divided into three the groups:no response group,the partial response group and the complete response group. We compared the complete remission rate(CR) between the three groups. χ2 test and Fisher exact test were performed with SPSS 17.0. Results:The stage of disease was changed in three patients(10.3%,3/29)on the basis of pre-treatment 18F-FDG PET/CT. CR rates of the no response group,the partial response group and the complete response group were 16.7%,69.2% and 80.0%,respectively(χ2 = 7.033,P = 0.030). CR rates of the complete response group and the partial response group were significantly higher than those of the no response group(χ2 = 4.310,P = 0.038;χ2 = 5.730,P = 0.017). Conclusion:18F-FDG PET/CT may be useful for clinical staging and assessment of chemotherapy response of middle stage in DLBCL.