s Background and Aim: Current study identified personality traits in addicted patients, members of narcotics anonymous (NA), addicts under methadone maintenance therapy, and non-addict as prediction factors of attempting and maintaining treatment. Methods: This descriptive cross-sectional study performed on totally 144 drug abusers, including 109 male addicted patients, members of narcotics anonymous (NA), addicts under methadone maintenance therapy and 35 non-addict males. Data was gathered by using the NEO Five-Factor Inventory- Revised (NEO-FFI-R) and analyzed by using ANOVA and post hoc Tukey test. Results: The highest personality traits, in NA group included openness, agreeableness, extraversion, neuroticism and conscientiousness respectively .In MMT group, neuroticism, openness, agreeableness, conscientiousness and extraversion were the highest personality traits. In addicted group: neuroticism, extraversion, openness, agreeableness and conscientiousness. In non-addicted group, agreeableness, extraversion, openness, conscientiousness, neuroticism were the highest personality traits. There was a significant difference in neuroticism between the MMT group, the addicted group and the MMT group with the non-addicted group. The addicted group had the higher score in this trait (p<0.05) compared with other groups. Conclusion: Among personality traits, neuroticism had the highest power to predict the treatment attempt and maintenance in addicted patients.
