Social support may play an important role in helping drug users achieve abstinence; however these benefits may depend on the type of support experienced. In this prospective observational study, we examined the extent to which general and abstinence-specific support, both structural and functional, predicted opiate and cocaine abstinence in 128 opioid maintenance patients receiving either methadone or LAAM. A new multidimensional self-report instrument assessing abstinence-specific functional support was developed for the study. Previously validated measures were used to assess the remaining types of support. With baseline abstinence and other statistically important covariates adjusted, hierarchical logistic regression analyses demonstrated that the associations between social support at study baseline and biochemically confirmed abstinence 3 months later varied by type of support and by drug. Greater abstinence-specific structural support (operationalized as fewer drug users in the social network) and decreases in three types of negative abstinence-specific functional support (Complaints about Drug Use, Drug Exposure, and Demoralization) predicted cocaine, but not opiate abstinence. There were no effects for general support, whether structural or functional, on abstinence from either drug. Interventions that focus on modifying patients' abstinence-specific support may be helpful in reducing the high rates of cocaine use disorders in this population.