Objective: Increased mortality from respiratory diseases was observed in epidemiological studies of patients with ulcerative colitis [UC] as a potentially underestimated extraintestinal manifestation. We therefore investigated the presence of pulmonary manifestations of inflammatory bowel disease [IBD] and the potential effect of tumour necrosis factor alpha [TNF-α] inhibitors on pulmonary function tests [PFT] in a prospective, longitudinal study. Methods: In all, 92 consecutive patients with IBD (49 Crohńs disease [CD], 43 UC) and 20 healthy controls were recruited. Fifty patients with IBD were in remission, and 42 had active disease with 22 of these being examined before and 6 weeks after initiating anti-TNF therapy. Pulmonary function tests [PFT] were evaluated using the Medical Research Council [MRC] dyspnoea index and a standardized body plethysmography. IBD activity was assessed using Harvey-Bradshaw index for CD and partial Mayo score for UC. Data are presented as mean ± standard error of the mean [SEM]. Results: Patients with active IBD showed significant reduction of PFT. Forced expiration [Tiffeneau index] values [FEV1%] were significantly reduced in IBD patients with active disease [78.8 ± 1.1] compared with remission [86.1 ± 0.9; p = 0.0002] and with controls [87.3 ± 1.3; p = 0.001]. Treatment with anti-TNF induced a significant relief in obstruction [p = 0.003 for FEV1% in comparison with baseline levels]. The level of pulmonary obstruction significantly correlated with clinical inflammation scores [HBI or Mayo]. Conclusions: Patients: with active IBD present with significant obstructive abnormalities in their PFTs. Obstruction is related to inflammatory activity, with anti-TNF improving PFTs. Pulmonary obstruction and possibly chronic bronchopulmonary inflammation is an overlooked problem in active IBD that is probably obscured by intestinal symptoms.