An association between chronic marginal periodontitis and chronic obstructive pulmonary disease (COPD) has been suggested. The aim of this study was to investigate whether chronic marginal periodontitis is more prevalent in very severe COPD than in other very severe respiratory diseases, and whether periodontitis in COPD is related to risk factors for periodontitis that are often present in COPD subjects. Orthopantomograms were collected from 130 patients with COPD and 50 patients with non-COPD evaluated for lung transplantation. Chronic marginal periodontitis was defined as a general marginal bone level > or = 4 mm. The prevalence of periodontitis was 44% in the COPD group vs. 7.3% in the non-COPD group. All oral measurements differed significantly between the groups. The difference in mean marginal bone level remained statistically significant when adjusting for age, gender and pack years smoked. In logistic regression analysis mean marginal bone level > or = 4 mm was identified as a factor significantly associated with severe COPD. This study demonstrates that chronic marginal periodontitis is common in patients with severe COPD. The high prevalence of periodontitis in COPD patients appears to be independent of possible risk factors for periodontitis such as age, pack years smoked, body mass index, use of corticosteroids and bone mineral density.