Purpose: To investigate the oral health behaviour and the smoking habits among diabetic adults with regard to diabetesrelated factors and their background information. Materials and Methods: In 2005, a questionnaire was conducted among diabetic adults (N = 299) in Tehran, Iran. The subjects were invited to the dental clinic and were asked to complete a self-administered questionnaire. In addition to their background information, the questionnaire requested information on smoking, oral self-care, dental attendance, year of onset of diabetes and organ complications related to diabetes. The data related to the type of diabetes and the latest value of glycosylated haemoglobin level (HbA1c) were obtained from the patient records at the diabetic clinic. Chi-square test and binary logistic regression model were used for statistical analyses. Results: Of all the subjects, 29% reported brushing their teeth on a twice-daily basis. Women (P = 0.05) reported higher frequencies of twice-daily tooth brushing. Subjects with moderate diabetic control (HbA1c = 7.6-8.5%) showed the highest rate for twice-daily tooth brushing (P 0.001). Of all the subjects, 47% reported having visited a clinician within the past 12 months; this rate was the highest among those without diabetes-related complications (52% versus 41%; P = 0.05). Subjects who had a physician referral were more likely to report having had a dental visit within the past 12 months (OR = 4.4; CI = 1.9-10.2). Conclusions: The present results call for improvement in the level of oral self-care and the regularity of dental checkups among diabetic adults to compensate for their increased risk for oral diseases. Palabras clave: diabetes mellitus, oral self-care, use of dental services