Background & Objectives: Chronic disease such as cancers and diabetes are leading causes of deaths and involved in psychological problems in patients with these illnesses. The mental health condition is one of the most effective factors in improving condition of these patients. This study was aimed to investigate and compare three psychological variables, self- concept, Locus control and defense mechanism and their interaction with each other in two diabetic and normal individuals groups.

  Methods: This study was done by comparison method. In this study 80 samples (40 diabetes and 40 normals) were selected by convenience sampling and matched and assessed by three standard questionnaires Rajers's self- concept, Ghamari's Defense mechanism and Rater's Locus of control. There are suitable validity and reliability for used questionnaires. The data analyzed by T student, chi-square and regression.

  Results: There was positive significant difference between self- concept and defense mechanism but no significant difference was found between two groups for a locus control. There was negative relationship between locus control and defense mechanisms.

  Conclusion: Regarding significant difference between two groups on investigated psychological variables, it is necessary to consider patients mental health by clinical staff in order to advance health in patients.