Among diabetic patients, oral health status and oral health behavior have been found to relate to metabolic control. The aim was to analyse which psychological characteristics, i.e. intention, self-efficacy, locus of control or self-esteem related to health behavior most comprehensively explain oral health habits, diabetes adherence, dental caries, deepened periodontal pockets, and the metabolic parameter HbA1c (glycosylated hemoglobin). The study subjects consisted of a group of 149 insulin-dependent diabetic patients. Data were obtained from self-completed questionnaires. The proportions of variance explained by the linear regression model were used as measures in the comparisons. It was found that oral health habits and diabetes adherence correlated. Both dental and diabetes self-efficacy scores were related to oral health habits and diabetes adherence. This indicates that self-efficacy is the best overall determinant of various health behavior practices. The ability of psychological characteristics to explain oral health was limited. Improvement of self-efficacy therefore may have a positive effect on various aspects of health behaviors.