Lymphangiomas result from abnormal development of the lymphatic system, with obstruction to lymph drainage from the affected area. The neck is the most common site (25%). In this study, we review the literature of lymphangioma in the neck and thorax and have undertaken detailed analysis of 52 children with cervical lymphangioma treated during the 20 years 1969-1988. Cervicomediastinal lymphangioma is uncommon (4%) and lesions confined to the thorax are rare, with none in our series. Neck lymphangiomas occur in early childhood with half being diagnosed at birth and almost 90% before school age. All have a mass. Two-thirds are asymptomatic; sudden enlargement, inflammation, infection, feeding difficulties and respiratory symptoms occur in the remainder. Pharyngeal and laryngeal involvement, usually associated with large infiltrating lesions, results in acute airways obstruction. The respiratory symptoms caused by mediastinal extensions are usually less dramatic. Lymphangiomas have a characteristic appearance on ultrasound examination and CT scan. These investigations are mandatory for an undiagnosed intrathoracic mass and when there is clinical suspicion of mediastinal extension of cervical lymphangioma but should be obtained for neck swellings only when the clinical diagnosis is in doubt. The recommended treatment is surgical excision which can be achieved with no mortality and little morbidity. An initial period of observation is justified for asymptomatic cervical lesions because there is a small incidence (6%) of spontaneous regression. Cervicomediastinal lymphangiomas can be removed at one operation using a neck incision combined with median sternotomy. The surgeon must preserve vital structures (especially vagus, recurrent laryngeal and phrenic nerves) and should not necessarily attempt total removal of all lymphangiomatous tissue. Massive infiltrating cervical lesions pose a particular challenge and may require multiple operations over many years before a satisfactory result with good-quality survival is attained.