Aims : To describe the use of high-resolution computed tomography (HRCT) in the multidisciplinary approach to patients with diffuse and interstitial lung disease; to describe characteristics on HRCT scans differentiating among definite usual interstitial pneumonia (UIP), probable UIP, indeterminate for UIP and an alternative diagnosis; to describe the role of HRCT in clinical decision making in patients suspected of having idiopathic pulmonary fibrosis (IPF) and to compare ATS/ERS/JRS/ALAT clinical guidelines with the Fleischner Society criteria for the diagnosis of IPF.