Substance abuse is a maladaptive pattern of substance use appearing through recurrent and significant adverse consequences related to the repeated use of substances. The aim of the present study was to examine the predicting role of impulsiveness and ego strength in medicinal, motivational and combined (medicinal-motivational) treatment of substance use disorder. For this purpose, 180 participations referred to 3 drug rehabilitation center and randomely assigened in each treatment group. All participants were asked to complete Barrat Impulsiveness Scale (BIS) and Ego Strength Scale (ESS) before startine the programmes. The results were analysed for the final number of participants in each group including medicinal (45), motivational (39), and combined (43). It was shown that the outcomes of the medicinal and mixed treatments were predicted by impulsiveness following 3 and 6 months interventions. Impulsiveness could not be able to predict results of the motivational intervention. It was also showed that the outcomes of the three models of treatment were predicted by ego strength following 3 and 6 months interventions. Based on the results of the present study, it can be concluded that considering influential psychological factors on addiction such as impulsiveness and ego strength, makes prevetional, diagnostic and therapeutic programmes more effective for substance use disorder.