Lymphangiohaemangiomas are rare congenital malformations, which on histological examination show both vascular and lymphatic elements. Clinically they tend to behave as lymphangiomas. Conservative management is usually recommended, with intervention only if vital structures are affected or if required for cosmetic reasons (Bruce Williams, 1981). Mediastinal lymphangiohaemangiomas are exceedingly rare and may require treatment because of their position. A case of benign lymphangiohaemangioma of the mediastinum is presented. Unlike the only previously reported case of computed tomography (CT) in this condition (Angtuaco et al, 1983), our case showed neither near-water density nor contrast enhancement following intravenous contrast medium administration. A girl of 2 years and 8 months was admitted to Queen Elizabeth Hospital, Hackney, with a discharging cervical tuberculous fistula. She was incidentally found to have a superior mediastinal mass. After treatment of her tuberculosis, at the age of 2 years and 10 months, an exploratory thoracotomy was performed at Great Ormond Street Hospital. The operative findings were of an irresectible tumour densely adherent to the pericardium and to the great vessels in both thoracic cavities. Histological specimens showed a complex vascular malformation predominantly of lymphangiomatous tissue but containing abnormal blood vessels, appearances consistent with a diagnosis of benign lymphangiohaemangioma. A subtotal resection was performed at the age of 3 years 4 months. The left phrenic nerve was noted to pass through part of the tumour and had to be resected. At 4 years and 7 months the patient presented with a persistent cough.