A 49-year-old man presented with a left nasal cavity mass, biopsy of which revealed extranodal NK/T cell lymphoma. A PET-CT scan showed increased F-18 FDG uptake in the nasal mass, anterior mediastinal lymph nodes, and multiple subcutaneous nodular deposits in the chest wall, gluteal region, and right femoral areas. The patient achieved complete remission with salvage L-asparaginase therapy after failing first-line standard anthracycline-based chemotherapy. PET-CT was very useful in detecting subcutaneous nodules consistent with widespread dissemination. There is limited literature data on the use of the PET scan in the diagnosis and staging of extranodal nasal NK/T-cell lymphomas. Our case highlights the important role of F-18 FDG PET in the staging of these patients.