The CT features of 12 patients with bronchiolitis obliterans organizing pneumonia (BOOP) were reviewed and correlated with clinical history, histologic specimens, and chest radiography. From our series, a spectrum of CT findings of parenchymal lung involvement in BOOP emerged. Focal nodular or mass-like opacities were found in 42% (5 of 12). Areas of consolidation resembling pneumonia were seen in 33% (4 of 12). Peripheral subpleural reticular opacities were identified in 25% (3 of 12). Patchy ground glass infiltrates were seen in 8% (1 of 12). One patient demonstrated a mixed pattern consisting of nodular opacities and areas of pneumonic consolidation. In 4 of the 5 cases demonstrating the nodular form of BOOP either a feeding vessel or bronchus sign could be identified. This feature consisted of a pulmonary vessel leading to a nodular opacity or an air bronchogram entering into a nodular opacity. Correlation of the CT findings of BOOP with histologic specimens showed nodular opacities and areas of consolidation to be associated with classic pathologic features of BOOP including bronchiolar plugs of granulation tissue and surrounding organizing pneumonia. Cases demonstrating peripheral subpleural reticular opacities showed, in addition to pathologic evidence of BOOP, other features such as interstitial disease and fibrosis.