BACKGROUND: Given the nature and chronicity of diabetes mellitus (DM), the role of self care and adequate patient education, in addition to the support of medical professional, is essential in its management. The aim of the present study was to compare the effects of positive messages and negative messages in DM education and to identify the superior method of motivation for self care behaviors. METHODS: A total of 99 DM patients (50 positive message group: 49 negative message group) at Gyeongsang National University Hospital participated in the study. The collected data were analyzed by Chi square and t-test. RESULTS: There were no significant differences in the attitude of messages and in the attitude of self care behaviors between the positive and negative message group, though the negative message group had a significantly higher intention of self care behaviors than did the positive message group. CONCLUSION: These results suggest that the negative messages are more effective than positive messages for increasing the intention of self care behaviors in patients with DM.