The authors report a clinical case of congenital cyst of the pancreas occurred in a female aged 15 months. They stress how this pathology is particularly rare in pediatric age (only 22 cases in the literature) and how it is extremely difficult to formulate a preoperative diagnosis. The young patient was in good general condition with an enormous abdominal tumefaction and without alterations of hematochemical markers. Echographic and tomographic patterns led to four diagnostic hypotheses: a) mesenteric cyst; b) left ovarian cyst or compound ovarian tumor; c) intestinal duplication; d) pancreatic cyst. Only after surgery a correct diagnosis was formulated (on the basis of the topographic position and the intracystic content of amylase and lipase) and a complete resolution of this pathology was obtained. Surgery therefore has the double function of formulating a correct diagnosis and allowing the complete resolution of this pathology. The complete surgical removal of the mass, in view of the benignity of this lesion, is the therapeutic goal.