We present CT, MRI and venography findings in 13-year boy with mediastinal fibrosis and superior vena cava (SVC) thrombosis associated with Behcet's disease. Fibrosing mediastinitis is an excessive fibrotic reaction that occurs in the mediastinum and may lead to compression of mediastinal structures (especially vascular). This condition is usually idiopathic, though many (and perhaps most) cases in the USA are thought to be caused by an abnormal immunologic response to Histoplasma capsulatum infection. SVC syndrome secondary to extrinsic compression by mediastinal fibrosis combined with Behcet's disease has rarely been described. Radiological investigations of this syndrome are necessary to avoid a useless anticoagulant therapy. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.