Mediastinal widening is a frequent radiological finding in the emergency department patient. The causes of mediastinal widening can be divided into traumatic and nontraumatic mediastinal widening. An important association of moderate to high velocity trauma is the mediastinal haematoma. It may be the result of traumatic transsection of the aorta, or it may be due to bleeding from other mediastinal vessels. Before the era of multidetector spiral CT, angiography was the gold standard for the evaluation of patients with a widened mediastinum. Meanwhile, angiography as a risk-carrying invasive examination has widely been replaced by MDCT. However, conventional radiography remains an important diagnostic tool; so does angiography, especially in the context of interventional radiology. Multidetector spiral CT plays an important role (Alkadhi et al., Radiographics 2004; 24:1239-1255), but usually as a second line procedure. This article discusses the radiological signs of traumatic mediastinal widening. Different traumatic lesions resulting in a widened mediastinum are presented, and some nontraumatic causes of a widened mediastinum are shown, in order to facilitate the differentiation between both entities.