To determine the value of helical computed tomography (CT) in the diagnosis, management and outcome of patients suspected of having descending necrotizing mediastinitis (DNM). Thirty-two patients with suspected DNM were submitted to contrast-enhanced single detector-row helical CT, four detector-row CT and 16 detector-row CT of the neck and chest. In 10/32 patients (group 1) no abnormality was observed in the neck or in the chest spaces on CT scan. These patients were all treated non-operatively. In 12/32 patients (group 2) CT showed the presence in the neck spaces of fluid collections, fasciitis, cellulitis, myositis, jugular vein thrombosis and lymphadenopathy; in all these patients the chest was unaffected. A cervical drainage was performed in ten patients. In the remaining ten patients (group 3), the neck infection involved the mediastinal spaces in all the cases and the pleural and pericardial spaces; CT findings included mediastinal cellulitis and fluid collections, pleural and pericardial effusions, venous thrombosis and lymphadenopathy. In these patients, a cervico-mediastinal drainage was performed and antibiotics were administered. The CT provides a highly accurate depiction of the presence and the spread of DNM. The CT findings and the extension of disease are important factors in order to predict for patient management and outcome.