Introduction: Drug abuse is a critical problem in the world and our country. There are various approaches that tries to study this problem. One of the important and useful approaches in this field is addiction as a brain disease. In this field, Gray,s Reinforcement Sensitivity Theory argues that brain systems has an important role in peoples tendency toward drugs. The aim of this study is investigating the role of behavioral activation system (BAS) and behavioral inhibition system (BIS) in peoples tendency toward opioids.Â Method: In this descriptive-correlational Study our sample included 43 male opioid abusers and 43 male controls without any history of drug use, as control group which completed BIS/BAS (Carver & white,1994) Questionnaire. Results: Logestic regression analysis of data shows that there are significant differences in BAS scores and Fun seeking scores between opioid users and control group. BAS with B=0/12 and Fun seeking with B=0/31 are two variables that can predict tendency toward opioids. That is High scores in this variables increases possibility of opioid abuse.Â Conclusion: The findings of this study shows that BAS and one of its subsystems (Fun seeking), can predict peoples tendency toward drug abuse. About behavioral inhibition system (BIS) there was no significant difference between opioid users and our control group.