The records of 23 patients diagnosed and treated at the Massachusetts General Hospital for extranodal non-Hodgkin's lymphoma of the paranasal sinus and nasal cavity were reviewed. The majority of patients were Ann Arbor stage I and approximately evenly divided in T1 or T2 (n = 10) and T3 or T4 (n = 13). Eight patients had nasal-type NK/T cell and 15 patients had diffuse large B-cell lymphoma (DLBCL). The patients with nasal-type NK/T cell lymphoma predominately involved the nasal cavity (5/8), whereas the DLBCL more often had the paranasal sinuses as the primary site (12/15). All patients received radiation as part of their treatment. Only three patients received chemotherapy as part of their initial treatment for three cycles using a cyclophosphamide, doxorubicin, vincristine, and prednisone-based regimen. By coincidence, the estimated overall survival (OS) and disease-free survival rates for both 5 and 10 years were all the same for all analyses. The OS for the entire group at 10 years was 78%. Significant prognostic factors were Ann Arbor stage IEA versus IIEA ( p = 0.0001) and T stage with (T1 or T2) versus (T3 or T4) (p = 0.0243). Combining Ann Arbor stage and T stage created a highly significant prognostic variable (IEA & [T1 or T2], IEA & [T3 or T4], IIEA & [T1 or T2], IIEA & [T3 or T4]) at p = 0.0001, regardless of site or histology. Patients with local-regional disease appear to be well controlled with radiation alone, but distant failure remains a problem. A combined-modality approach with local-regional radiation and systemic chemotherapy is recommended for these patients.