Abstract： Objective To investigate the prognostic value of interim and post-therapy 18fluorine-fluododeoxyglucose(18F-FDG) PET-CT in patients with T-cell lymphoma.Methods A retrospective analysis was conducted on data from 50 patients diagnosed with T-cell lymphoma(12 patients underwent interim PET-CT only,19 patients underwent interim and post-therapy PET-CT,and the rest 19 patients underwent only post-therapy PET-CT).Interim and post-therapy PET-CT(positive versus negative) were visually interpreted according to the criteria of the International Harmonization Project.The progression-free survival (PFS) and overall survival(OS) of two groups were calculated.We used the Fisher exact test and KaplanMeier testfor data analysis.Results Interim 18F-FDG PET-CT results were positive in 19 cases and negative in 12 cases.The median PFS and OS were 8 months and 16 months,in patients with positive results,versus 30 months and 36 months,in patients with negative results.The 1-year PFS and 3-year OS rates were 21.1％ (4/19) and 10.5％(2/19) in patients with positive results at interim PET/CT versus 100.0％(12/12) and 66.7％ (8/12) in patients with negative results(P＜0.01.Post-therapy 18F-FDG PET-CT results were positive in 16 cases and negative in 22 cases,the median PFS and OS were 10 months and 20 months in patients with positive results versus 32 months and 41 months in patients with negative results.The 1-year PFS and 3-year OS rates were 12.5％(2/16) and 12.5％(2/16),in patients with positive results at post-therapy PET-CT versus 95.5％(21/22) and 54.5％(12/22),in patients with negative results(P＜0.01).Conclusion Both interim PET-CT status and post-therapy PET-CT have significant value in monitoring response to therapy and predicting prognosis for patients with T-cell lymphoma.