The authors compared measures of process and six-month outcomes for 45 individuals who were treated in a long-term residential treatment program for patients with dual diagnoses with measures for 39 individuals who were treated in a short-term program. They also compared outcomes for individuals within each group. Those who received long-term treatment experienced improvements between entry into the program and six-month follow-up, and they were more likely to have engaged in treatment than individuals in the short-term group. At follow-up, individuals in the long-term residential treatment group were more likely to have maintained abstinence and less likely to have experienced homelessness than those in the short-term group.