Mesenchymatous hamartoma is a benign liver tumor characteristically found in childhood, particularly during the first two years of life. A case of mesenchymatous hamartoma detected in a 23-year-old female during a study for non specific abdominal disturbances is presented. Imaging techniques showed a large mass in the right hepatic lobe with hypodense areas of cystic appearance. Pathologic study demonstrated the characteristic mixoid mesenchymatous component with areas of cyst formation and rests of liver tissue inside the tumor. Despite its rarity in adults this case demonstrates the need to consider mesenchymatous hamartoma in the differential diagnosis of hepatic masses in adults, particularly when radiologic examination demonstrates cystic components.