Thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) are the major catabolic enzymes of 5-FU. In this study, we analyzed the concentration of TP and DPD in non-small cell lung cancer tissue by enzyme-linked immunosorbent assay. We measured the TP and DPD levels in 25 adenocarcinoma tissues and 25 squamous cell carcinoma tissues. The mean TP concentration in non-small cell lung cancer tissue was statistically higher than that of normal lung tissue as was the mean DPD concentration. The ratio of the TP level to DPD level in tumor tissue was higher in squamous cell carcinoma than in adenocarcinoma. No significant difference could be detected between the TP level, DPD level, or TP/DPD level and the tumor size or lymph node metastasis. In conclusion, chemotherapy with 5-FU may be more effective in squamous cell lung cancer patients than lung adenocarcinoma patients from the result of the ratio of TP to DPD.