The value of high-resolution computed tomography (HRCT) in diagnosing and assessing inflammatory activity in sarcoidosis is well established. The aim of the present study was to address the intra- and inter-observer agreements of the HRCT score by Oberstein et al. [8], and to evaluate the relationship between HRCT findings and disease severity expressed in respiratory functional impairment in sarcoidosis. The clinical records of 80 known sarcoidosis patients visiting the outpatient clinic between January 2000 and August 2001, who underwent a HRCT as well as lung function tests (including exercise testing), were reviewed. Two readers scored the first 60 HRCT images twice. Weighted kappa and intra-class correlation coefficient were used to assess the reliability of the HRCT scoring system. Spearman's rank correlation coefficients and multiple regression analyses were performed to evaluate the relationship between HRCT findings (first reading, reader A) and respiratory functional impairment. Intra- and inter-reader reliability demonstrated good agreement. All HRCT subscores, except enlargement of lymph nodes, were correlated to the FEV(1), FVC, DLco, Pao(2)max (all p<0.05) and A-aPo(2 )max ( p<0.001). Furthermore, HRCT abnormalities, but not the chest radiographic stage, were strongly associated with functional parameters. Abnormal changes of lung parenchyma, established by HRCT features, were associated with respiratory functional impairment in sarcoidosis. Moreover, compared with the radiographic stages, HRCT findings appeared to be much more sensitive in depicting respiratory disability, especially abnormal gas exchange.