Cisplatin-based concurrent chemoradiotherapy (CCRT) has become a standard treatment for cancer of the uterine cervix. However, there have been no investigations into the optimum timing for administration of anticancer drugs using animal models. The aim of the present study was to determine the appropriate timing for administration of the anticancer drug cisplatin in relation to delivery of radiation by assessing the antitumor activity and adverse effects of 3 different regimens in αT3 transgenic mice bearing lens epithelial tumors. CCRT showed the strongest antitumor activity. There was a significant difference between CCRT and administration of cisplatin before radiotherapy (neoadjuvant therapy) with regard to the apoptotic effect detected by TUNEL staining, but there was no significant difference between CCRT and administration of cisplatin after radiotherapy (adjuvant therapy). Assessment of adverse effects showed that there were no significant differences in the mortality rate, weight loss, anemia and leukopenia among the 3 regimens. In conclusion, these findings obtained in an animal model suggest that cisplatin should probably not be administered before irradiation, since the antitumor effect is significantly weaker than that of CCRT or administration after irradiation, while adverse effects are similar.