BACKGROUND AND PURPOSE: Abnormalities of the chest wall have been described in bronchopulmonary dysplasia (BPD). Clinical, radiographic and pulmonary function variables were evaluated in 1-year-old children ventilated because of neonatal lung disease in order to quantify these thoracic changes and to evaluate the lung disease. METHODS: The pulmonary status of 51 infants with neonatal lung disease requiring artificial ventilation was reevaluated clinically and radiographically at the age of 1 year. Twenty-two of these infants had developed BPD. Thoracic depth and width were measured clinically and on chest X-ray. The Toce score evaluated the presence of cardiomegaly, hyperinflation, emphysema and interstitial lung disease. Lung function was measured after sedation using previously reported methods. In BPD patients, Toce score and lung function were determined and compared at 1 month and at 1 year of age. RESULTS: In BPD patients, chest depth was significantly smaller when measured clinically as well as on chest radiograph (P < 0.05; Mann-Whitney U-test). There was a statistically significant correlation between chest depth measured clinically and on chest X-ray. Toce score was significantly higher in BPD patients (P < 0.05). In BPD patients intersitial abnormalities and decreased lung compliance were more frequent at the age of 1 month than at the age of 1 year. At the age of 1 year, hyperinflation was more frequent and at that time increased airway resistance was still noted. Thus the type of X-ray abnormality reflects the type of lung function disturbance. CONCLUSION: The flatness of the chest is most likely a consequence of the long-standing lung function abnormalities.