To study the role of anomalous pancreatico-biliary ductal union (APBDU) in the development of choledochal cyst, we reviewed 23 cases. APBDU is defined as a long common channel(>0.4 mm). The patients ages ranged from 1 week to 112 months and the mean age was 22.5 months. Right upper quadrant pain was the most prevalent symptom. The diagnosis was made by ultrasonography and operative cholangiography in most patient. The preoperative diagnosis was made in 100 % of the cases. Gallstones were found in 5 cases. Todani type I and type IV were prevalent. A long common channel was found in all cases. The operative treatment consisted of cyst excision and Reux-en-Y hepaticojejunostomy or choledochojejunosotmy. One patient had postoperative pancreatitis. There was no mortality. We conclude that detection of choledochal cyst is occurring at a younger age and APBDU seems to play an important role in the pathogenesis of type I and IV cysts. Cyst excision is the treatment of choice to eliminate repeated cholangitis and malignant transformation.