To encourage the public to attend and accept oral cancer screening, further understanding is required of the ability of structured information to alter patient knowledge and risk perceptions. Previous work has shown the benefit of written information for those at high risk of oral cancer, especially for tobacco smokers. This study investigated three hypotheses: first that a patient information leaflet (PIL) would enhance risk perceptions, and second that the effect of the leaflet on knowledge would be confirmed as in previous studies and third that these improvements would be associated with smoking behaviour. Patients (N = 995) attending 20 general dental practices in Northern Ireland were invited to participate, 28 refused (response rate = 97%). Patients were randomised into two groups. The experimental group received a PIL and then completed a self-report questionnaire, whereas the control group followed same procedure without the PIL. Measures included a 36 item oral cancer knowledge scale and two items to assess risk perception. Usable data were available from 944 patients; mean (SD) age = 42 (15), 65% female. Risk perceptions of oral cancer were minimally effected by the PIL (p = 0.023). This effect was demonstrable in smokers. Smokers were sixteen (95% CI: 8-30) times more likely to believe that they were at greater risk of oral cancer than non-smokers. A clear benefit of the PIL on patients' oral cancer knowledge was found, particularly for smokers and those with a history of smoking. These findings demonstrate that public awareness of smokers can be raised with written information although health beliefs such as risk perceptions require more intensive intervention.