Superior vena caval syndrome (VCS), is easily recognised in the advanced case, however in the early case without clinical signs its detection is much less easy. New techniques of medical imagery such as IRM and above all computer tomography (TDM) have shown an increasing place in the daily clinical practice of the respiratory physician; these enable an early diagnosis to be made and a work up of the aetiology of the syndrome of VCS. With TDM the obstruction of the VCS appears the sign of direct obstruction (thrombosis or extrinsic compression) and of a collateral venous circulation deriving some anastomoses from the brachio-cephalic venous trunk (TVBC) and the azygos system, the VCS and the inferior vena cava (VCI), the two TVBC at the junction of the median line principally by the suprasternal network and finally these portal systemics, by the veins from the anterior wall of the trunk and the accessory portal veins of the round ligament. IRM introduced more recently enables a direct vision of the causal lesion endo or extra luminally, enabling an early detection of the syndrome by showing signs of a slow down of the venous flow. But the detection of a collateral circulation seems more difficult to demonstrate by this method.