The purpose of this study was to describe thin-section CT findings of lung involvement in patients with primary Sjögren's syndrome (PSS), and to correlate them with pulmonary function tests (PFT). The chest thin-section CT examinations of 35 patients with proven diagnosis of PSS and respiratory symptoms were retrospectively assessed by two observers, in a first step independently with interobserver evaluation, and in a second step in consensus. The extent of the most frequent CT findings was scored. Correlation was made with PFT in 31 of these patients. Three main CT patterns were identified with good interobserver agreement (kappa coefficient 0.71): 19 of 35 (54%) large and/or small airways disease; 7 of 35 (20%) interstitial lung fibrosis (ILF); and 5 of 35 (14%) suggestive of lymphocytic interstitial pneumonia (LIP). The CT scans were normal in 2 patients (6%) and showed only dilatation of pulmonary vessels due to pulmonary arterial hypertension in two others (6%). Airway disease patients had predominantly obstructive profiles (mean FEV(1)/FVC ratio 69.7+/-12.7%, mean MEF(25) 50.1+/-22.9%), whereas patients with ILF and LIP had predominantly restrictive profiles and/or a decreased diffusing lung capacity (mean TLC 87.0+/-26.0 and 64.6+/-18.6%, mean DL(CO) 57.4+/-21.2 and 52.0+/-8.0%). Significant correlation ( p<0.01) was found between the scores of ground-glass attenuation and TLC ( r=-0.84) and DL(CO) ( r=-0.70) and between the score of air trapping and FEV1 ( r=-1.0). In patients with PSS and respiratory symptoms, thin-section CT may provide characterization of lung involvement which correlates with pulmonary function.