A duodenal duplication cyst is rare congenital anomaly, which accounts for 5% of all gastrointestinal duplication cysts. Most of the duodenal duplication cysts are usually found during infancy or early childhood, and present with obstructive symptoms. The most common clinical manifestations are an intestinal obstruction or, less commonly, hemorrhage, perforation, biliary obstruction or pancreatitis. The traditional treatment of a duodenal duplication cyst has been complete surgical resection, but very few cases of endoscopic treatment of a duodenal duplication cyst have been previously reported recently in the literature. Moreover, endoscopic treatment of a duodenal duplication cyst has not been reported in Korea. We report our first experience of a duodenal duplication cyst, including diagnosis and endoscopic management with a detachable snare. (Korean J Gastrointest Endosc 2007;35:190-195)