Background and objectives: Co-morbidity of psychiatric disorders and substance abuse disorder have extensive effects and is accompanied by poorer prognosis. Treatment of this population should be proportionate to their needs. Current study aims to survey personality disorders among referrers to the addiction treatment center, thereby may contributes in achieving a more comprehensive view on encountering them and their treatment.

  Methods: In this cross-sectional descriptive study, number of 100 persons with substance abuse disorder were selected by convenient sampling method from referrers to the Reference Center of Addiction Treatment of Ardabil province in 2008. Necessary information was gathered by researcher designed questionnaire (including demographic information) and Million's questionnaire of Personality Disorder. And gathered data were extracted and analyzed by SPSS Software.

  Results: Results analysis showed that the most observed associated disorders in the studied subjects was the Antisocial Personality disorder (0.54%) and Borderline, Histrionic and Narcissistic Personality disorders were located at next ranks, respectively. There was no significant relationship between used drug type and duration of usage to specific personality (p > 0.05). There was significant statistical difference between multi-drug and one-drug abusers addicts, from view point of having or not having personality disorder (p < 0.05).

  Conclusion: Results analysis showed high co-morbidity of personality disorders and drug abuse among addicts (84 %) and lower rate of personality disorders among persons with one drug compared with multi-drug abuse.