By far the most common cystic lesion of the pancreas is the inflammatory pseudocyst. Among the true cysts the mucinous neoplasm is unique because of its proliferative natura and the potential for carcinomatous degeneration. Hence establishment of the diagnosis prior to surgical exploration is of great importance. The imaging characteristics of ultrasonography and computed tomography are particularly useful in the preoperative differentiation of mucinous cystic neoplasms from pseudocysts of the pancreas. This report descrives the ultrasonographic and computed tomographic findings of eight mucinous neoplasms(three cystadenoma five cystadenocarinoma) and twenty four pseudo-cysts. Mucinous cystadenomas are well-defined large multilocular cystic masses containing irregu-lar thick speta solid components and locally thickened wall. Sonographic and computed tomographic findings of cystadenocarcinomas are similar to those of cystadenoma but cys-tadenocarcinomas frequently show daughter cysts along the primary cystic wall locally inva-sion and distant metastasis. Pseudocysts are unilocular cystic masses which walls are uniform in width contanining many debris within the cysts and are often located at extrapancreatic areas.