Lymphangiomas are rare cystic tumours that may present as cystic masses in the retroperitoneum. Retroperitoneal lymphangiomas account for approximately 1% of all lymphangiomas. Confusion with other cystic tumours of the retroperitoneum including those arising from the liver, kidney and pancreas is common. A case of a retroperitoneal cystic lymphangioma occurring in a 41-year-old woman raising interesting diagnostic and management issues is reported. The patient presented with vague abdominal pain and persistent nausea. Radiological imaging demonstrated a large multiloculated thin-walled cyst involving the upper retroperitoneum. Surgical resection was complete, revealing a benign cavernous lymphangioma. The patient made a complete recovery and was disease-free 30 months postoperatively.