A 43-year-old woman complaining of upper abdominal pain was referred to our clinic. Well movable mass was detected in the right hypochondria region by palpation. Three years before, she underwent cholecystectomy and choledochotomy for cholelithiasis. After that she had been aware of painless mass in the right hypochondria region, but because of no symptom she regarded it as operative scar and had no treatment. Abdominal CT, ultrasonography, upper GI series and barium enema revealed a retroperitoneal cyst compressing the 3rd portion of the duodenum upward and the vena cava backward. Laparotomy showed an unilocular chylous cyst, 5 cm in diameter in the retroperitoneal cavity. Histologically, the cyst was cystic lymphangioma. Etiologically, the previous operation of cholecystocholedocholithiasis was supposed to be a trigger of the development of the chylous cyst.