OBJECTIVE To provide indications for high-resolution computed tomography (HRCT) of the chest in patients with cystic fibrosis (CF). METHODS We compared the HRCT and conventional chest radiography (CCR) scores and assessed their correlation with clinical scores and pulmonary function tests. METHODS Department of Pediatrics, Federico II University, Naples, Italy. METHODS A total of 30 patients with CF 6.75 to 24 years of age. RESULTS CCR scores correlated highly with HRCT (r = -0.8) and clinical (r = 0.5) scores, whereas total HRCT scores were not related to clinical scores. Of all the specific HRCT findings, only bronchiectasis appeared related significantly to the clinical score (r = 0.6). Most pulmonary function tests were related to CCR and total HRCT scores, but not to HRCT scoring of specific changes. Forced vital capacity and CCR scores appeared the best predictors of the HRCT score (multiple R = 0.58 and 0.79, respectively). In patients with mild lung disease, HRCT detected bronchiectasis and air trapping in 57% and 71% of the cases, respectively. In patients with more abnormal chest radiographs, bronchiectasis and air trapping were demonstrated on HRCT in all cases. CONCLUSIONS These findings suggest that HRCT of the chest is most useful in the identification of early lung abnormalities in patients with CF with mild respiratory symptoms, whereas for established disease, CCR is still the first-line imaging technique. The advantage of detecting early changes on CT imaging awaits additional confirmation, at least until early therapeutic interventions affecting significantly the final outcome of the disease are demonstrated. In patients with advanced disease, HRCT may be useful in the evaluation of specific lung changes when more aggressive treatment such as chest surgical interventions is indicated. Given the cost of the procedure and the high radiation dosage compared with CCR, a careful assessment of the cost:benefit ratios of HRCT is strongly recommended in CF.