The role odiagnosed ENKL. The SUVmax may provide additional prognostic information for IPI and KPI.f (18)Fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) in extranodal natural killer/T-cell lymphoma (ENKL) is not well established. This study aimed to investigate the prognostic role of the pretreatment maximum standardized uptake value (SUVmax) on PET/CT in patients with newly diagnosed ENKL. Among 364 consecutive patients with newly diagnosed ENKL, 81 patients were included and reviewed. The impact of SUVmax on survival and the relationship between SUVmax and other clinicopathological parameters were analyzed. The median SUVmax was 14.6 (range 2.0-45.4). The optimal cutoff value of SUVmax to predict overall survival (OS) was 15. Patients with high SUVmax (SUVmax > 15) were associated with bulky disease (P<0.001), local invasion (P = 0.030), high score of Korean Prognostic Index (KPI, P = 0.046), resistance to primary treatment (P = 0.014), poor OS (P<0.001), and unfavorable progression-free survival (P<0.001). With a median follow-up of 25.0 months, the median OS was 63.0 months (range 2.0-99.0 months). Multivariate analyses revealed the following independent prognostic factors for OS: age > 60 years (P = 0.001), stage III-IV (P = 0.023), SUVmax > 15 (P = 0.020), and bulky disease (>5 cm) (P = 0.002). By using the SUVmax, patients in most subgroups stratified by the KPI or the International Prognostic Index (IPI) were further discriminated in OS with significant statistical difference. Our results suggest the pretreatment SUVmax is predictive of prognosis in patients with newly