Vascular anomalies, including hemangiomas and vascular malformations, comprise 3% to 6% of mediastinal masses in childhood. These lesions, whether in the mediastinum or elsewhere, often are misdiagnosed and treated inappropriately. Correct diagnosis almost always can be established by history, external physical examination of associated anomalies, bronchoscopy, and/or radiographic studies. Hemangiomas are benign tumors that involute spontaneously but may require antiangiogenic therapy or laser ablation to maintain airway patency prior to involution. Vascular malformations, most commonly lymphatic in origin, will not involute nor respond to drug therapy. Resection and/or sclerotherapy often are indicated.