Objective To investigate the prognostic value of pretreatment 18F-fluorodeoxyglucose (FDG) PET/CT imaging on extranodal nasal type natural killer/T-cell lymphoma (ENKTL).Methods Thirtyfive patients (20 males,15 females,average age 45 years) diagnosed as Ann Arbor stage Ⅰ-Ⅱ ENKTL from February 2013 to February 2016 were retrospectively analyzed.All patients were pathologically confirmed and underwent 18F-FDG PET/CT before treatment.The maximum standardized uptake value (SUVmax),international prognostic index score (IPI),serum lactate dehydrogenase (LDH),and immunohistochemical results were recorded.Patients were followed up for 2 years.The relationships between SUVmax,progression-free survival (PFS),pathological features and IPI were assessed using Fisher exact test.Results There were 18 ENKTL patients with progression,and 17 had no progression.Patients with SUVmax ≥ 12.2 had worse prognosis than those with SUVmax＜ 12.2 (P =0.001).There were correlations between SUVmax and Ki-67 (r=0.701,P=0.001),SUVmax and CD56 (r=0.393,P=0.032),SUVmax and IPI (r=0.787,P＜0.01),respectively.It was also found that SUVmax,Ki-67,CD56 and IPI were related to PFS (all P＜0.05).Conclusion SUVmax of 18F-FDG could be used as an important prognostic indicator for early ENKTL.