A study of 18 cases of mediastinal hemangiomas is presented. The patients were eight women and 10 men between the ages of newborn to 74 years. Clinically, the most common symptoms included dyspnea, cough, and chest pain. In one patient the mediastinal hemangioma was associated with another hemangioma in the gastrointestinal tract and presented initially with gastrointestinal bleeding. Four patients were asymptomatic. Anatomically, 14 tumors were located in the anterior mediastinum and four in the posterior mediastinum. Surgical resection was the treatment of choice for all patients. Grossly, the lesions were described as well circumscribed, cystic, hemorrhagic tumors that ranged in size from 2 cm to 20 cm in diameter. Histologically, the tumors were divided into two groups, one showing the features of capillary hemangioma characterized by a lobular and solid growth pattern featuring dilated small vessels and a solid proliferation of endothelial cells and another group showing the features of cavernous hemangioma characterized by large dilated vascular spaces with areas showing interstitial inflammatory changes, fibrosis, and smooth muscle proliferation. A few tumors were characterized by prominent regressive changes, including stromal hyalinization, dystrophic ossification, cystic and perivascular myxoid changes, and extensive fatty overgrowth. Some of the tumors showed extreme cellularity with virtual obliteration of vascular lumina due to compression by tumor cells and focal mitotic activity similar to that observed in cutaneous juvenile hemangiomas. Despite their large size, often infiltrating appearance, and sporadic mitotic activity, follow-up ranging from 1 month to 4 years in 11 patients showed all to be alive and well, thus demonstrating the benign nature of these neoplasms. A discussion of the differential diagnosis and a review of the literature on these rare tumors are presented.