We describe two cases of primary thyroid lymphoma, involving 64-and 74-year-old women who presented with arapidly growing palpable mass in the anterior neck. In both patients, plain radiographs of this region re-vealedtracheal displacement and soft tissue mass, and CT scans demonstrated the presence of a large soft tis-sue masswith homogeneously low attenuation, predominantly located in the unilateral lobe of the thyroid g-land. Within themasses there was no calcification, necrosis, or hemorrhage, though in one patient the trachea was involvedposteriorly by the mass Both masses appeared as cold nodules on RI scan, and in both patients, the final diagnosiswas diffuse large cell type non-Hodgkin's lymphoma with a background of Hashimoto's thyroiditis.