Objective To explore the clinical value of 18F-FDG PET/CT in evaluation of curative effect on diffuse large B-cell lymphoma(DLBCL).Methods 18F-FDG PET/CT was performed before and after 6 cycles of chemotherapy(R-CHOP or CHOP protocol) in 34 patients.By measuring maximum SUV(SUVmax)and maximum diameter(Dmax),the clinical value of PET and CT were compared in evaluation of curative effect on DLBCL after chemotherapy.Twelve patients underwent PET/CT examination for three times:before treatment,after 2 cycles of chemotherapy and after 4 cycles of chemotherapy.SUVmax and Dmax were compared among three groups.All the 8 patients who have reached complete response and 10 patients who have reached partial response after 6 cycles of chemotherapy were followed-up,and then the one-year progression-free survival (PFS) was observed.Results ①There was significant difference between SUVmax and Dmax before and after 6 cycles of chemotherapy on DLBCL patients(t=3.58 and 2.96,both P＜0.05).② There was significant difference among before,after 2 cycles of chemotherapy,after 4 cycles of chemotherapy in SUVmax and Dmax (F=18.64 and F=4.33,both P＜0.05).There was significant difference of SUVmax between before and after 2 cycles of chemotherapy (t=5.37,P＜0.05),and no difference of Dmax(t=l.05,P＞0.05).There was significant difference of both SUVmax and Dmax between before and 4 cycles of chemotherapy (t=8.56and 3.90,both P＜0.05).③Among 8 patients who have reached complete response,6 cases were PFS＞1,2cases were PFS＜1.Among 10 patients who have reached partial response,2 cases were PFS＞1,8 cases were PFS＜1.Conclusions In evaluation curative effect on malignant DLBCL during and after treatment,PET was significantly better than CT.PET/CT as combination of PET with CT had a higher clinical value to evaluate the therapeutic effect of DLBCL.