Many people learn about smoking cessation through information on the Internet. Whether people with severe mental illnesses, who have very high rates of smoking, are able to use currently available websites about smoking cessation is unknown. The study reported here assessed whether four smoking cessation websites met usability guidelines and whether they were usable by smokers with severe mental illnesses. Four websites that appeared first on a Google search and represented an array of sponsors were selected. First, five experts rated the websites on adequacy of content in six areas and usability in 20 areas. Second, 16 smokers with severe mental illnesses performed two search tasks on the websites with researchers observing their searches and interviewing them regarding usability. One of the websites was rated by experts as acceptable for content and usability, but most of the participants were unable to navigate this website. The only website that was navigable received poor content ratings by experts. Four easily accessible websites did not meet the needs of smokers with severe mental illnesses. Although the Internet is a promising strategy to provide education about treatments, website developers must attend to the needs and capacities of multiple user groups.