Duplications of the gastro intestinal tract are characterised (Ladd and Gross) by the following histological features two muscular layers with myenteric cells inside. Cystic or tubular, they are always situated on the mesenteric border of the gastro intestinal tract with a common blood supply. The pathogenesis of duplication affects early fetal development via various mechanisms. Located anywhere along the alimentary tract as in our review of 12 cases, clinical manifestations vary according to the site. Abdominal cystic mass, mediastinal compression or intestinal obstruction bleeding or perforation are possible symptoms, but the presentation is very variable. The age of presentation is usually within the first year of life. The diagnosis can be made preoperatively by several investigations but the malformation is frequently discovered during surgery. Surgery is the only treatment for these duplications, but smaller cystic lesions are easily treated. However surgery of extensive duplications remains difficult.