Background: Among the etiological and precipitating factors in tendency to use drugs, psychological variables and personality traits are of particular importance in relation to drug abuse. This study was carried out in order to assess not only different dimensions of temperament and character in opiates and amphetamines-dependent patients but to examine any existing relationship between these dimensions and the abused substance. Materials and methods: In this survey correlation study, 46 amphetamine and 50 opiates-dependent subjects who referred for treatment to Aftab clinic in the city of Mashahd (a North-Eastern city in Iran) were selected. Subjects were administered Cloninger's Temperament and Character Inventory (TCI-56). The data were analyzed using SPSS v.21.T-Test was used to compare the mean of the groups. Results: The subscales of the temperament scale including novelty seeking, harm avoidance, reward dependence, persistence and the subscales of the character dimensions including cooperativeness and selftranscendence scores were higher in amphetamine-dependent individuals than in opiate-dependents. Conclusion: Our findings revealed significant differences between the personality traits of opiates and amphetamine-dependent individuals. ORIGINAL ARTICLE مجله / علوم پزشکی دانشگاه آزاد اسالمی و ی ژگ ی های آمفتام و متادون با درمان تحت معتادان ی ن ه ا م جله علوم پزشکی اسالمی آزاد دانشگاه د وره 92 شماره ، 4 ، زمستان 28 ، صفحات 942 تا 953