Introduction: Poorly reversible airflow obstruction may or may not be related to smoking. Objectives: To describe patients with severe obstructive lung disease including etiology, imaging, functional aspects, systemic manifestations, and the pattern of bronchodilator response. Methods: Sixty-eight patients (age 55.9 +/- 13.7 years, FEV1 [forced expiratory volume in one second] 31.9 +/- 10.2% predicted) underwent spirometry, evaluation of body mass composition, 6-minute walk test, X-ray, thorax high-resolution CT scanning, and clinical evaluation. Results: Of 68 patients enrolled, 37 had chronic obstructive pulmonary disease (COPD) and 31, extensive bronchiectasis. Among COPD patients the CT scans showed emphysema in 78.4%, and bronchiectasis in 48.6%. There were no significant differences between smokers and nonsmokers, except for vital capacity, significantly smaller in non-smokers (p<0.001). We found 29 and 20 volume responders (VR) according to Pare et al. (FEV1/FVC > 1 = flow responder or <1 =VR) and ATS/ERS criteria, respectively. According to Pare et al. criteria, there were 18 patients with FEV1 <30% predicted among 29 VR, and 12 with FEV1 <30% predicted among 39 without volume response (p=0.0101). Conclusions: In patients with severe obstruction, smoking does not appear to be relevant in determining functional or systemic differences, and Pare et al. criteria can detect more VR. Bronchiectasis is a common finding in severe COPD. (C) 2012 Sociedade Portuguesa de Pneumologia. Published by Elsevier Espana, S.L. All rights reserved.1911318