The chemosensitivities of squamous cell carcinoma (SCC) tissues from the head and neck area were compared to findings of adenocarcinoma, mainly from digestive organs. The sensitivity of each tissue was determined using the in vitro succinate dehydrogenase (SD) inhibition test, which shares a common principle with the 3-(4,5-dimethyl-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Tumor tissues were obtained at surgery or biopsy. Anticancer drugs tested were carboquone, Adriamycin, mitomycin C, cisplatin (CDDP), aclacinomycin A, 5-fluorouracil and 1-hexylcarbamoyl-5-fluoro-uracil with 10 times the peak plasma concentration, respectively. The means ± standard deviations of SD activities in SCC tissues were significantly lower than those in adenocarcinoma tissues (p < 0.001), and the sensitivity rates of SD activity in SCC tissues had a higher value than those in adenocarcinoma tissues (p < 0.05), against each drug. Our study showed that CDDP-based combination regimens might be effective for SCC tissues. The chemosensitivity of each excised tissue should be tested, in order to prescribe sensitive, effective drugs for each patient.