<p><b>OBJECTIVE</b>To analyze the prognostic related factors of elderly patients with T/NK cell lymphoma.</p><p><b>METHODS</b>The clinical data of 62 T/NK cell lymphoma patients with age over 60 years and treated in Shanghai Jiaotong University Medical School affiliated Ruijin Hospital from 1999 to 2011 were collected and analyzed. Multivariate and univariate analysis of clinical data were performed using a COX regression model, including stage, performance status, extranodal infiltration, bone marrow involvement and LDH level. According to IPI or PIT systems, survival functions were estimated using the Kaplan-Meier method and compared by the log-rank test.</p><p><b>RESULTS</b>Using the IPI system, the CR rate of the low risk (IPI = 1, n = 7), intermediate-low risk (IPI = 2, n = 22), intermediate-high risk (IPI = 3, n = 13) and high risk (IPI = 4-5, n = 20) groups were 85.7%, 59.1%, 0% and 5.0%, with the median overall survival (OS) of 90.0, 63.9, 10.1 and 5.0 months, respectively. The patients with IPI = 1-2 had significant longer OS than those with IPI = 3-5 (P < 0.01), but no significant difference of OS was observed between IPI = 1 and IPI = 2 (P = 0.3647). As for the PIT system, CR rate of patients with PIT = 1 (n = 18), PIT = 2 (n = 18) and PIT = 3-4 (n = 26) were 61.1%, 44.4% and 3.8%, with the median survival of 90.0, 46.9 and 5.0 months, respectively. Significant difference of OS was found among groups of PIT = 1, PIT = 2 and PIT = 3-4 (P < 0.01). Therefore, PIT index was more effective than IPI in predicting prognosis of elderly T/NK cell lymphoma patients. The significant parameters of the univariate analysis were B symptom (P = 0.025), increased LDH level (P = 0.004), bone marrow infiltration (P = 0.023) and extranodal involvements (P = 0.033). Multivariate analysis showed that only increased LDH level (P = 0.007) and bone marrow involvement (P = 0.016) were the two independent prognostic factors of survival. These two factors were included in PIT index.</p><p><b>CONCLUSIONS</b>PIT is more effective than IPI to predict outcomes of elderly T/NK lymphoma patients.</p>