Because of a mutual association between severity of periodontitis and poor control of IDDM, regular dental visits and daily oral care are important among diabetics. The aim was to develop a method for analysing dental self-efficacy and to study the relationship between dental self-efficacy and reported oral health behaviour and oral hygiene. The relationship between oral health behaviour and HbA1c level was also studied. Data were collected in relation to 149 IDDM patients by means of a quantitative questionnaire, evaluation of dental plaque and patient records. Results showed that tooth brushing self-efficacy, approximal cleaning self-efficacy and dental visiting self-efficacy related to corresponding reported oral health behaviour (p<0.0005). Visible plaque index (VPI) correlated inversely with tooth brushing self-efficacy (r(s) = -0.208, p = 0.012) and dental visiting self-efficacy (r(s) = -0.240, p = 0.004). Approximal cleaning self-efficacy correlated with age (r(s) = 0.225, p = 0.006) and dental visiting self-efficacy was related to higher professional level of education (p = 0.009). Those having better tooth brushing self-efficacy (p = 0.020), higher frequency of tooth brushing (p = 0.032) and lower VPI (p<0.0005) had better HbA1c level. It was concluded that perception of dental self-efficacy plays a decisive rôle in relation to oral health behaviour in diabetic patients, and that compliance with dental recommendations is also related to HbA1c level.