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Given the importance of drug addiction, this article aims to study the current relationship between personality disorders and types of drugs used (narcotics and stimulants) in Iranian addicts. The sample consisted of 285 drug addicts including 132 narcotic addicts and 153 stimulant addicts selected randomly in several phases. Data collecting process was accomplished by means of clinical interviewing based on DSM-IV criteria for addiction, Addiction Severity Index (ASI), and Millon Clinical Multiaxial Inventory – III (MCMI-III). Using Pearson correlation coefficient and regression, the gathered data were analyzed. There was a significant correlation between stimulant consumption and histrionic personality disorder (p