CT findings were reviewed in 68 patients with untreated head and neck lymphoma. More than half of the patients with either Hodgkin's disease or non-Hodgkin's lymphoma were detected in the earlier stages (stage I or II). Four types of abnormalities were identified with CT: nodal involvement alone (type 1), extranodal involvement alone (type 2), a combination of extranodal and nodal disease (type 3), and multifocal extranodal disease with or without nodal involvement (type 4). In the 18 patients with Hodgkin's disease, a subgroup of mixed cellularity was most common; type 1 was the prevailing CT presentation, and no type 2 or 4 lesions were observed. In the 50 patients with non-Hodgkin's lymphoma, diffuse large-cell lymphoma was the most common histologic subtype, and the most common CT presentation was type 2, followed by type 3. Lymphomatous nodes may be extensive and confluent, but often they are smaller than 2 cm and rarely are necrotized. The most frequent extranodal sites of head and neck lymphomas are Waldeyer's ring, paranasal sinuses, and nasal cavity. Extranodal lymphoma cannot be differentiated reliably from the more commonly occurring carcinoma, although it is less often associated with invasion and destruction of adjacent bony structures. Multiple sites of extranodal involvement, with or without neck lymphadenopathy, may suggest a diagnosis of non-Hodgkin's lymphoma.