Background & Aim: Addiction not only results in some serious physical problems, but also results in social and economical problems for countries. On the other hand, adolescence is the most risky period for Substance Abuse. Therefore, understanding predisposing factors related to addiction could due to a purposefully planned program for prevention and follow up. The purpose of this study was the effect of instructional classes on adolescent's knowledge from predisposing factors related to addiction.

Materials & Methods: This research was a semi experimental study has been done at Hamedan pre university centers. In this study 220 female students in two groups (case –control) have taken part. They are selected in randomly branch. The tool of assessment was a questionnaire that was provided by researcher. Case and control groups answered the questions then interaction performed at 20 minute. Finally, level of their knowledge about predisposing factors of addiction evaluated again. All statistics computed by the SPSS software.

Results: results showed that knowledge score in control group was not significant in test re test (p>0/05) but there was a meaningful difference in case group before and after interaction (p=0 /00, t= -20/3).Before interaction only7/5 percent in control group and 3/8 percent in case group have very good knowledge (p=0/00) but after interaction 6/6 percent in control group and 84 percent in case catch it.

Conclusion: In this study, most adolescences knowledge about predisposing factors of addiction increased significantly after intervention. Therefore, such instructional classes are very important for them.