High-resolution computed tomography (HRCT) has an established role in the detection and differential diagnosis of chronic diffuse infiltrative lung disease. Available data suggest that, in certain cases, HRCT may also be used to determine the presence or absence of, and extent of, abnormalities that are likely to reflect potentially reversible (acute or active) lung disease, as compared with irreversible (fibrotic) lung disease. In doing so, HRCT permits an assessment of disease prognosis. Furthermore, because HRCT can accurately identify subtle active lung disease, it may be used to monitor the success or failure of treatment. This article reviews the HRCT features associated with potentially reversible, as compared with irreversible, lung disease, and the accuracy with which these features can be used to predict disease activity and prognosis in chronic diffuse infiltrative lung disease and therefore assist management.