In this review, the contribution of high resolution computed tomography (CT) to the diagnosis of pulmonary sarcoidosis, the possible role of CT in defining reversible disease, and the potential use of CT to obtain pathophysiological insights are discussed. The role of CT in the diagnosis of sarcoidosis remains contentious, as the CT manifestations of sarcoidosis are highly variable, and typical appearances are often associated with a classical clinical and chest radiographic profile. The greatest diagnostic utility of CT lies in difficult cases of diffuse lung disease, especially advanced disease; sarcoidosis can often be excluded with confidence when CT appearances are pathognomonic of an alternative disorder (such as extrinsic allergic alveolitis, lymphangitis carcinomatosis, or fibrosing alveolitis). CT patterns indicative of reversible and irreversible disease have been identified, through CT-histological correlations and serial imaging studies; a nodular pattern is almost invariably reversible, reti-cular abnormalities and anatomic distortion denote and irreversible fibrotic histological picture, ground-glass opacification is variably reversible and may be indicative of alveolitis or fine fibrosis. However, CT influences therapeutic decisions in a minority of cases in clinical practice. The potential use of CT to gain pathophysiological insights is discussed briefly.