Diagnostic imaging in patients with acute respiratory distress syndrome (ARDS) has an important role both for research and clinical purposes. In this review we discuss the role of chest radiograph and computed tomography (CT) as diagnostic imaging tools in ARDS. Chest radiograph remains the simplest, most efficient and routinely available method to assess the status of the lung parenchyma in the intensive care unit setting. However, although chest radiography gives an estimation of the general severity of the disease, CT scan provides more specific and detailed information. CT scan needs the transfer of the patients to scanning suites, which, if carefully organized, is not associated with increased morbidity. In our opinion, CT scan should be always performed in patients with ARDS in the early and late phase of the disease to define 1) the severity and distribution of the disease related to its specific etiology; 2) the morphologic changes of the lung parenchyma with time; 3) the regional distribution of recruitable and ovestretched lung regions with different ventilatory settings; and 4) the presence and evolution of iatrogenic and nosocomial complications. These informations may be extremely useful to select an appropriate ventilatory treatment, to improve diagnostic capabilities, and to monitor the clinical course of the patient. Further studies are needed to better define the role of CT scan in the daily clinical management of ARDS.