Abstract Background: High-resolution computed tomography has proven to play a basic role in the detection and characterization of various pulmonary lesions (interstitial, small air way disease etc.) in patients with collagen vascular diseases. Accurate HRCT detection of pulmonary involvement in collagen vascular disease has important therapeutic and prognostic implications. Aim of Study: The aim of this study is to evaluate role of HRCT in diagnosis of thoracic manifestation of collagen vascular diseases. Patients and Methods: 100 patients diagnosed as collagen vascular disease were referred to Radiology Department in Faculty of Medicine, Cairo University for HRCT of the chest. Results: Interstial lung disease was seen in 48 patients (48%), while 31 patients (31%) showed signs of small airway disease. Conclusion: HRCT is fundamental for evaluation of all thoracic manifestation of collagen vascular diseases.