Descending necrotizing mediastinitis (DNM) is an uncommon disease and may be lethal if not treated adequately and promptly. In all settings, multidetector row computed tomography (MDCT) is the most valuable tool to assess the presence and extension of the disease when DNM is clinically suspected. The key point for an accurate diagnosis of descending necrotizing mediastinitis is to establish the pathway of spreading of the neck soft-tissue infection to the mediastinum on axial and reformated multidetector row computed tomography images. The aims of this article are to describe the relevant anatomy of the pathways of neck infection to the mediastinum; to analyze the most characteristic computed tomography features of DNM, and to discuss the impact of computed tomography in the management and in the surgical therapy of these patients.