The association of progressive obliterative bronchiolitis (OB) with rheumatoid arthritis (RA) is uncommon but has been reported previously. Diffuse panbronchiolitis (DPB) is a unique inflammation principally affecting the respiratory bronchioli and has been reported mainly in Japanese adults. Recently, DPB has also been noted in patients with RA in Japan. Therefore, there might be considerable overlap in clinical features between DPB and OB associated with RA in Japan. The aim of this study was to evaluate the clinicopathological characteristics of bronchiolitis in patients with RA. Three RA patients clinically diagnosed as having DPB were evaluated. All patients underwent chest radiographs, pulmonary function tests (PFT) and post mortem examination. Clinical features in all patients were a history of productive cough, exertional dyspnoea, wheezing and/or coarse crackles. Chest radiographs showed small nodular shadows up to 2 mm in diameter with bronchiolectasis throughout both lungs in all patients. The PFT revealed marked obstructive impairment in all patients. All patients died of progressive respiratory failure. Pathologically, two out of the three cases were confirmed as DPB, while the remaining one case was confirmed as OB, because the primary obstructive lesions were in the respiratory bronchioli in the former and in the membranous bronchioli and the proximal small bronchi in the latter. Thus, the clinical features of DPB and OB were strikingly similar, but the histopathological features revealed distinct differences. This study demonstrated that there was considerable overlap in clinical features between diffuse panbronchiolitis and obliterative bronchiolitis associated with rheumatoid arthritis, suggesting that diffuse panbronchiolitis might be a new manifestation of rheumatoid arthritis. The differentiation of these two disease entities is significant in making decisions on their therapeutic modality and is possible by analysing the precise histopathological findings of the lung.