We report a very rare occurrence of a primary collision tumor in the lung consisting of squamous cell carcinoma and T-cell lymphoma. A squamous cell carcinoma was diagnosed histologically following a transbronchial lung biopsy in a 71-year-old woman, but the other component was diagnosed histologically and immunohistochemically only on examination of the resection specimen. The malignant lymphoma was stained by the monoclonal antibody UCHL-1 (anti-D45RO) against T-lymphocytes but was not stained by the L26 (anti-CD20) antibody against B-lymphocytes. Immunostaining for CD3 was positive, confirming a T-cell lineage. Despite systemic chemotherapy, the patient died 7 months after operation, from progression of the lymphoma. Our case, which illustrates interesting attributes of collision tumors, consisted of an ordinary squamous cell carcinoma and a rare T-cell lymphoma arising in the lung, with the latter part of the combination dictating subsequent treatment and outcome.