We describe a case of lung tumor in a 33-year-old woman with tongue cancer. She had noticed a painful sensation in her tongue in April 2000. The results of a physical examination showed a 22× 11 mm ulcerated lesion on the right side of her tongue. A biopsy specimen showed a moderately differentiated squamous cell carcinoma. A preoperative chest radiograph showed no evidence of pulmonary metastasis. No neck lymphadenopathy was found. The tongue cancer was resected in September 2000, and the pathological stage was T2 N0 M0. A solitary pulmonary lesion appeared 8 months after the surgery. A Histological examination of a transbronchial lung biopsy specimen showed a moderately differentiated squamous cell carcinoma. It was difficult to distinguish histopathologically or immunohistochemically between a second primary tumor and a metastasis, but the pulmonary lesion was considered to be a second primary tumor on the basis of a single endobronchial lesion that appeared after the T2 tongue cancer with no regional recurrence or cervical lymphadenopathy. Treatment with chemotherapy and irradiation was not effective and the patient died 3 months after the diagnosis of lung cancer.