Severe thoracic sarcoidosis includes manifestations with significant clinical and functional impairment and a risk of mortality. Severe thoracic sarcoidosis can take on various clinical presentations and is associated with increased morbidity. The purpose of this article was to describe the CT findings in severe thoracic sarcoidosis and to explain some of their mechanisms. Subacute respiratory insufficiency is a rare and early complication due to a high profusion of pulmonary lesions. Chronic respiratory insufficiency due to pulmonary fibrosis is a frequent and late complication. Three main CT patterns are identified: bronchial distortion, honeycombing and linear opacities. CT can be helpful in diagnosing some mechanisms of central airway obstruction such as bronchial distortion due to pulmonary fibrosis or an extrinsic bronchial compression by enlarged lymph nodes. An intrinsic narrowing of the bronchial wall by endobronchial granulomatous lesions may be suggested by CT when it shows evidence of bronchial mural thickening. Pulmonary hypertension usually occurs in patients with end-stage pulmonary disease and is related to fibrotic destruction of the distal capillary bed and to the resultant chronic hypoxemia. Several other mechanisms may contribute to the development of pulmonary hypertension including extrinsic compression of major pulmonary arteries by enlarged lymph nodes and secondary pulmonary veno-occlusive disease. Aspergilloma colonization of a cavity is the main cause of hemoptysis in sarcoidosis. Other rare causes are bronchiesctasis, necrotizing bronchial aspergillosis, semi-invasive pulmonary aspergillosis, erosion of a pulmonary artery due to a necrotic sarcoidosis lesion, necrosis of parenchymal sarcoidosis lesions and specific endobronchial macroscopic lesions.