The purpose of this study was to assess the knowledge diabetic patients have of their risk for periodontal disease, their attitude towards oral health and their oral health-related quality of life (OHRQL). One hundred and one consecutive patients (age range 31–79 years) recruited from a diabetic outpatient clinic participated in the study. Twenty-seven per cent of participants had type 1 diabetes, 66% type 2 and 7% did not know what type of diabetes they had. The length of time since participants were diagnosed as diabetic ranged from 1 to 48 years. Metabolic control of diabetes as determined by HbA1c levels ranged from 6·2% to 12·0% compared with the normal range of 4·5–6·0%. Thirty-three per cent of participants were aware of their increased risk for periodontal disease, 84% of their increased risk for heart disease, 98% for eye disease, 99% for circulatory problems and 94% for kidney disease. Half of the participants who were aware of their increased risk for periodontal disease had received this information from a dentist. Dental attendance was sporadic, with 43% reporting attendance within the last year. OHRQL was not significantly affected by the presence of diabetes in the group surveyed, in comparison with a previous survey of non-diabetic patients. A significant association was found between metabolic control and dentate status. Awareness of the potential associations between diabetes, oral health and general health needs to be increased in diabetic patients.