Forty-four patients affected with cystic fibrosis (CF) were examined by means of high-resolution Computed Tomography (HRCT) of the chest; the sensitivity of this technique was evaluated in identifying small pulmonary structure alterations, and its role outlined. In all cases, HRCT scans allowed early lobular shape anomalies to be detected and secondary pulmonary lobular lesions to be correlated with disease evolution. A classification for lobular lesions was proposed: Stage I - Thickening of the bronchovascular bundle and/or intralobular septa and/or middle interstitial compartment. Unessential changes in lobular ventilation. Preservation of lobular shape. Stage II - Intralobular emphysema. Acinar filling with normal ventilation (A) or diffuse hypoventilation of the lobule (B). Preservation of lobular shape. Stage III - Lobular consolidations. Preservation of lobular shape. Stage IV - Patch distribution of lesions characterized by derangement of lobular structures. Changes in normal lobular shape. The identification of these lesions confirms HRCT as the most sensitive technique for the early visualization and localization of signs of CF bronchopneumonopathy. A broader experience coming from the systematic use of HRCT in chronic inflammatory lung diseases would increase our knowledge of pathogenetic processes and allow therapeutic perspectives to be improved.