The idiopathic interstitial pneumonias are diffuse lung diseases characterized by interstitial inflammation and fibrosis. High resolution computed tomography (HRCT) is the best imaging technique for the study of interstitial disease. The general term "idiopathic interstitial pneumonia" includes usual interstitial pneumonia/idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, desquamative interstitial pneumonia, respiratory bronchiolitis-associated interstitial lung disease, cryptogenic organizing pneumonia, acute interstitial pneumonia, and lymphocytic interstitial pneumonia. The radiologist's role consists of identifying the macroscopic morphological pattern and working together with clinicians and pathologists to generate an integrated clinical diagnosis. The objective of this article is to review the idiopathic interstitial pneumonias and to describe their different manifestations in HRCT.