The Internet provides an easy and accessible way to deliver medical information about the management of various diseases, both to practitioners and to their patients. As there is no control over who posts information on the Web, there is a risk that the interests of the web producer may bias the quality of information. The quality of medical information on the management of chronic obstructive pulmonary disease (COPD) on the Internet was evaluated, comparing non-commercial and commercial websites. An internet search was conducted to locate relevant websites using a metasearch engine. The quality of websites was scored on a scale of 0–10, based on three items about the credibility of the site and seven items about the accuracy of the information provided by the site. Quality differences between commercial and non-commercial websites were explored. The search revealed 23 relevant websites (12 non-commercial and 11 commercial). The overall quality of non-commercial websites was better than that of commercial websites (median score 7 vs. 4, p= 0.01). Compared to commercial sites, non-commercial websites more often provided information about cessation of smoking (100% vs. 64%, p= 0.03), preventative influenza vaccinations (42% vs. 9%, p= 0.07) and use of long-term oxygen therapy (92% vs. 45%, p= 0.02). Among websites providing information on COPD, commercial sites were much more likely to be of poorer quality compared to sites of non-commercial organizations. In particular, commercial sites do not provide information about simple preventative treatments. There is a need to be vigilant about the quality of health information about COPD on the Internet.