The purpose of this study was to define distinctive clinical features of "nasal" and "nasal-type" NK/T cell lymphomas by assessing prognostic factors. The anatomic definition of extranasal NK/T cell lymphoma has been vague resulting in variable definitions of extranasal sites by different groups. We analysed the clinical behavior of 90 NK/T cell lymphoma patients and attempted to elucidate the prognostic factors for risk-based stratification of therapy. We observed no significant difference between "nasal" and "nasal-type" NK/T cell lymphomas in regards to clinical features and survival using the conventional anatomic classification. We suggest the categorisation of the two subtypes of NK/T cell lymphoma as follows: UNKTL (upper aerodigestive tract NK/T cell lymphoma) including all lymphomas confined to nasal cavity, nasopharynx, and the upper aerodigestive tract and EUNKTL (extra-upper aerodigestive tract NK/T cell lymphoma) group to include all sites other than the UNKTL group. The EUNKTL group in this study had advanced stage at diagnosis, higher LDH, higher IPI score, poorer performance and inferior response to the anthracycline-based chemotherapy with statistical significance. There was a significant difference in survival rate between EUNKTL and UNKTL group (20.0%, 54.0%, respectively, P = 0.0068). More aggressive treatment should be sought for this particular group of patients for EUNKTL patients.