PURPOSE: To evaluate lung parenchymal change as seen on chest radiographs and high-resolution CT (HRCT) afterthe resolution of adenovirus pneumonia (a common cause of lower respiratory infection in infants and children),and the usefulness of HRCT during follow-up. MATERIAL AND METHODS: Four to 13(mean, 8) months after recovery, tenpatients infected with adenovirus pneumonia underwent HRCT and chest radiographs. Eight were boys and two weregirls, and their mean age was 26(range, 14-45) monthes. Adenovirus pneumonia had been confirmed by viral isolationin culture or serologic test. CT scanning was performed during quiet breathing ; collimation was 2mm and theinterval from apex to diaphragm was 5-10mm. Lung settings were 1600 HU (window width) and -700 HU(level). CTfindings were assessed and compared with chest radiographs by two chest radiologists, who reached a consensus. Thepatients were clinically followed up for one year. RESULT: On chest radiographs, hyperlucent lung was seen in 8of 10 patients (80%) ; in one other there was partial collapse, and in one, findings were normal. The most commonHRCT finding was a mosaic pattern of lung attenuation with decreased pulmonary vascularity in the area of lowerattenuation ; this was seen in 8 of 10 patients (80%). Other findingss were partial collapse, bronchiectasis, andbronchial wall thickening, each seen in two patients, and reticulonodular density, seen in one. In two patientsHRCT findings were normal ; in one of these, chest findings were noraml but a mosaic pattern of lung attenuationwas found in all lobes. During follow-up, three patients wheezed continously. CONCLUSION: In cases of adenoviruspneumonia, HRCT demonstrated more specific parenchymal change than did chest radiographs ; a mosaic pattern oflung attenuation was seen, with decreased pulmonary vascularity in areas of lower attenuation ; bronchiectasis,bronchial wall thickening, and reticulo-odular density were also noted. These findings were presumably due tobronchiolitis obliterans, a well known complication of adenovirus pneumonia, and are prognostically helpful.