Retroperitioneal lymphangioma is an uncommon benign tumor. Most of the cases are found incidentally at surgery, autopsy, or lymphangiography. It could be suspected by CT and ultrasound if multiple septated loculated fluid collections found, and confirmed by fine-needle percutaneous aspiration. We report a case of retroperitoneal lymphangioma who was diagnosed preoperatively by CT, ultrasound and sono-guided aspiration of 150 ml chylelike fluid.