Background: Massive unilocular intraabdominal cysts in children are rare. Alimentary tract duplications can present diagnostic and therapeutic difficulties. Although they can occur anywhere from the mouth to the anus, they are commonly seen in relation to the ileum. We herein present an unusual case of duplication cyst itself occupying virtually all of the available intraabdominal volume. It appeared to be an enteric duplication cyst of ileal origin. Case Report: A 3-month-old girl was admitted to our hospital for investigation of progressive abdominal distension and biliary vomiting. Plain radiography of the abdomen showed normal air-fluid level in the stomach and paucity of gases in rest of the abdomen. Magnetic resonance imaging showed a huge, homogenous cyst extending from the xiphisternum down to the pelvis. The cyst was excised completely. Macroscopic examination and histologic findings confirmed the diagnosis of a huge enteric duplication cyst arising from the ileum. Conclusions: Enteric duplication cyst should be considered in a patient with an abdominal cystic mass. Radiologist must take into account patient age, clinical parameters, and imaging findings to identify the likely etiology of a cystic mass.