In the past, choledochal cysts had been infrequently diagnosed prior to surgical exploration for obstructive jaundice. However, with the advance of imaging modalities, preoperative diagnosis is usually apparent. We evaluated the radiological findings of choledochal cysts in 14 patients in whom ultrasonography (US) or computed tomography (CT) were mainly used for diagnosis. In addition, oral cholecystography, intravenous (i.v.) cholangiography, scintigraphy, and percutaneous transhepatic cholangiography were performed in some of them. The diagnosis was confirmed surgically in all patients. Ultrasonographic examinations were diagnostic in 13 of 14 patients. Preoperative specific diagnosis of choledochal cyst was possible with the demonstration of direct entrance of the extrahepatic bile ducts into the cyst in most cases. When US fails to show relation of cystic mass with biliary system, other imaging modalities can be used to clarify the findings.