Benign cystic lesions of the retroperitoneum and mesenterium are rarely encountered clinically 1, 2 . Up to 40% of such cysts are found incidentally during abdominal surgery for unrelated disorders 1 . Most patients display some chronic symptoms that necessitate therapeutic intervention. CT scan might help in confirming the diagnosis and surgery is the mainstay treatment. This report describes a case of a giant retroperitoneal cyst successfully excised in an adult female.