Novel antipsychotics have altered treatment expectations and outcomes for patients with severe forms of schizophrenia. A growing number of studies have assessed the effects of oral risperidone in persons with dual disorders. Potential mechanisms of action by which risperidone and other atypical antipsychotics could decrease substance use include being less likely to cause extrapyramidal side effects than typical agents, improving negative symptoms and ameliorating a dysfunction of the brain reward system. Risperidone long-acting injectable medication addresses issues of noncompliance, while avoiding peak blood levels of oral preparations, thereby minimizing EPS and improving negative symptoms of schizophrenia. Risperidone may also facilitate dopamine neurotransmission in the prefrontal cortex and correct a hypothesized dysfunction of the brain reward system.