The overall aim of this project is to use an advanced brain imaging technique, PET, in order to monitor the progress of pharmacotherapy with modafinil or topiramate for cocaine dependence in methadone-maintained patients who use cocaine in addition. Comparisons will be made within the cocaine dependent methadone maintained subjects, between the start and end of treatment, and between the two medications. This is the first systematic research study of pharmacological treatment for cocaine dependence in Israel. This study is of major clinical use, with implications for the treatment of cocaine dependence in poly-drug abusers in Israel. Successful pharmacotherapy for cocaine dependence is expected in reduction in cue-induced subjective craving and in glucose metabolism in brain areas elicited by cocaine craving. Metabolic activity in regions that are activated by craving should be correlated with dopamine DRD2 receptor occupancy in all patients.