Mucinous cystic neoplasms of the pancreas are uncommon and known to occur mainly in middle-aged women. Wepresent a case of pancreatic mucinous cystadeno-carcinoma in an 11-year-old girl who had a past history of bluntabdominal trauma. The tumor was initially mistaken for a traumatic pseudocyst. US and CT revealed a multiloculatedcystic mass in the pancreatic tail. The mass showed good transmission on ultrasonography (US) and had anattenuation value of 10 HU on CT. Metastatic lesions in the liver were also shown on follow-up study.