Associations have been found between diabetes status and periodontal diseases and dental caries. In addition to biological explanations, psychological features can be proposed to affect the relations between oral health and IDDM (=insulin-dependent diabetes mellitus). The aim of this study was to evaluate the psychological features characterizing oral hygiene practices, dental visiting and diabetes self-care. The research population consisted of 149 IDDM patients, and cross-sectional data were collected by a quantitative questionnaire, in clinical examinations and from patient records.There was a positive correlation between the sum scores for dental self-efficacy and diabetes self-efficacy and, correspondingly, between the dental and diabetes locus of control beliefs. High self-esteem was found to associate with good adherence to some specific health behaviors, such as tooth brushing, exercising and insulin adjustment. When Weiner´s attribution theory was used, there were similarities in the causal thinking in oral and diabetes view. All in all, especially the perception of self-efficacy was found to be a powerful feature characterizing health behavior. There were overlapping relations showing an association of high dental self-efficacy with good diabetes adherence, of high diabetes self-efficacy with frequent dental visiting, and of good metabolic control with high tooth brushing self-efficacy, frequent tooth brushing and low plaque level. On the basis of these results, enhancement of self-efficacy appears important.These results suggest that there might, indeed, be some common psychological features for both oral health behavior and diabetes self-care. These could partly explain the relations between diabetes status and periodontal diseases and dental caries. The results can be utilized in patientcentered health education by identifying and enhancing the psychological features that characterize health behavior and health status. The results emphasize the need for co-operation between dental and diabetes health care professionals in their daily practice.