A 76-year-old man presented with abdominal pain and constipation for 1 month. The pain was dull aching in nature and over the right upper abdomen. He also reported decreased appetite. The patient had no previous attacks of acute pancreatitis or history of trauma. There was no history of fever or melena. On visual inspection of the abdomen, there was a mass effect protruding out of the right mid-abdomen. The mass was approximately measuring 15×15 cm, firm in consistency, non-tender, non-mobile and not moving with respiration. Haematological investigations were normal. Both amylase and lipase were within normal limits. A CT of the abdomen revealed a large well-defined thin-walled cystic lesion measuring 10.3×13.9×14.3 cm in the right lumbar and iliac region without calcification or haemorrhage. A diagnosis of retroperitoneal cyst was made and the patient was taken up for surgery. Histology of the cyst showed the absence of epithelia and was reported as pseudocyst.