Chest CT has major advantages over conventional chest radiographs, including improved contrast resolution, tissue characterization capability, and cross-sectional anatomic display. For ICU patients, these advantages are counterbalanced by the need to transport such patients outside the ICU environment and also by increased expense and radiation dose. Most of all, chest CT is usually not necessary in ICU patients. The authors conclude that CT is especially helpful in patients whose clinical course is not explained by the available information or whose chest radiographs are difficult to interpret.