Despite a paucity of data, cystadenocarcinoma of the pancreas has been considered to be resistant to chemoradiation, with a limited effect similar to that of the more common pancreatic adenocarcinoma. We describe a case of a partially excised cystadenocarcinoma with a positive surgical margin that was treated by neoadjuvant chemoradiation. No epithelial elements were found on histologic examination after reresection. Three previous cases of dramatic response of pancreatic cystadenocarcinoma to chemoradiation have been described in the literature. The current dogma alleging poor response of pancreatic cystadenocarcinoma to chemoradiation may be in error.