A newborn boy had a severe, unexplained apnoea. On clinical examination a palpable abdominal mass was found extending over the right hemiabdomen. Further investigations by Ultrasound, CT scan and MRI revealed a liver tumor (7 x 5 x 9 cm). Histology from an open liver biopsy confirmed the diagnosis of a benign mesenchymal hamartoma. Operative resection of the tumor was performed when the patient was 2 1/2 months old. Postoperative management and clinical follow-up for twelve months were without complications. Primary liver tumors are rarely found in children. About half of them are malignant and associated with high mortality rates (e.g.hepatoblastoma). The most common benign liver tumors are mesenchymal hemangiomas and hamartomas. In this group of tumors prognosis has improved mainly due to progress in imaging techniques and progress in liver surgery during recent years.