Backgrounds & Aims: This research was done to determining the relationship between anti social personality and use of defensive mechanisms in Farabi hospital and the jail of Kermanshah city.
 
Material‚ and Methods: In a descriptive- analytic study, 50 people anti social at Farabi hospital and the jail of Kermanshah city were selected by available sampling by clinical interview, and 3- Milon test about defensive were studied. The statistical approaches and indicators, such as frequency, percentage, average, standard deviation and correlation coefficient were used to data analysis.
Results: Results indicated that there was a meaningful relationship between immature defensive mechanism and antisocial personality disorders (P=0.018). It means that if immature defensive mechanism is increased, the score of antisocial personality disorders will enhance, too. But, there was any meaningful relationship between neurotic defensive mechanism (P=0.401) and illogical and mature defensive Mechanism (P=0.909) with antisocial personality disorders.
 Conclusion: People with antisocial personality disorders apply immature defensive mechanism more than personality defensive mechanisms.