Objective: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease. The prognostic factor currently used is not accurate enough to predict the outcomes of patients with DLBCL. The prognostic significance of interim PET/CT in DLBCL remains controversial. The aim of this study is to determine the predictive value of interim 18F-FDG PET/CT after first-line treatment in patients with DLBCL. Methods: Thirty-two patients with DLBCL underwent baseline, interim and post-treatment 18F-FDG PET/CT scans. Imaging results were analyzed for the survival of patients via software SPSS 13.0, retrospectively. Results: Thirty-one of the 32 patients were treated with R-CHOP regimen, and interim 18F-FDG PET/CT of 24 patients was performed after 2 cycles of treatment. After a median follow-up period of 16.7 months, the 2-year progression-free survival (PFS) rates were significantly different between the groups above and below SUV max cut-off value of 2.5 (P=0.039). No significant differences were found in the 2-year PFS rates if SUV max cut-off values were set as 2.0 and 3.0, respectively (P=0.360; P=0.113). Conclusions: Interim PET/CT could predict the prognosis of DLBCL patients with the SUV max cut-off value of 2.5, but more clinical data should be concluded to confirm this conclusion. The prognostic factor currently used is not accurate enough to predict the outcomes of patients with DLBCL. The prognostic significance of interim PET / CT in DLBCL remains controversial. The aim of This study was to determine the predictive value of interim 18F-FDG PET / CT after first-line treatment in patients with DLBCL. Methods: Thirty-two patients with DLBCL underwent baseline, interim and post-treatment 18F-FDG PET / CT scans. Imaging results were analyzed for the survival of patients via SPSS 13.0, retrospectively. Results: Thirty-one of the 32 patients were treated with R-CHOP regimen, and interim 18F-FDG PET / CT of 24 patients was performed after 2 cycles of After a median follow-up period of 16.7 months, the 2-year progression-free survival (PFS) rates were significantly different between the groups above and below SUV max cut-off values ​​of 2.5 (P = 0.039) differences were f ound in the 2-year PFS rates if SUV max cut-off values ​​were set as 2.0 and 3.0, respectively (P = 0.360; P = 0.113). Conclusions: Interim PET / CT could predict the prognosis of DLBCL patients with the SUV max cut-off value of 2.5, but more clinical data should be concluded to confirm this conclusion.