Substance abuse is an important hygienic, psychic and social problem in the world. Gabapentin is a new antiepileptic drug that is used in neurological and psychiatric disorders. Moreover, the effects of gabapentin on increasing the analgesic effect of morphine and its inhibitory effect on dopamine release due to morphine in animal models have been proved. In the present study, the effect of gabapentin on withdrawal signs and symptoms in opium-addicted subjects and on psychiatric disorders and electroencephalogram of these patients during the detoxification period have been investigated. Two groups of patients were selected randomly. The first group (n= 36) received the current drugs based on their withdrawal symptoms and the second group (n= 35) received 300 mg gabapentin every 8 hours additionally. All patients were evaluated by electroencephalography and SCL-90 test on first and last days of hospitalization and their demographic characteristics were gathered by using a general questionnaire. During the hospitalization period (10 days) all subjects were assessed for withdrawal symptoms and signs. The analysis of data showed the excellent effect of gabapentin on all psychiatric symptoms and in decreasing signs and symptoms significantly. Gradual decrease of withdrawal symptoms and signs in the second group shows the efficacy of gabapentin. There was no significant difference between the two groups in regard to the electroencephalogram indices. The results showed that gabapentin improves the quality of therapeutic management in opium-addicts during the detoxification period.