A Sizeable sector of the population in Iran continues to use substance abuse despite government efforts to prevent addiction. Present study was designed to compare personality characteristics of addicts with non  addicts.

          One hundred and six addicts who sought treatment at addiction rehabilitation department of Hamadan , were recruited in this study. A selective control group matched for demographic variables with the first group were also requested to take part in the study. The structured clinical interview for DSM-IV and MMPI were administered.

          The results showed that patients in studied group represented a significantly different personality characteristics in contrast to the control group. Overal 77.8%of addicts were diagnosed as mental disorder. This figure for control group was 26.2% . Also 41.3% of addicts were diagnosed as personality disorders, while the figure for non addicts was 5.8%.

          High rates of mental disorders and personality problems are reported for addicts. It Seems that psychiatric symptoms and psychological vulnerabilities have important role in addictive behavior.