BACKGROUND: Improving services and treatment outcomes for individuals with cooccurring alcohol and drug use disorders and psychiatric conditions has been a critical challenge to clinicians and policy makers. This study examined 1-year outcomes for individuals entering chemical dependency (CD) treatment with and without cooccurring psychiatric diagnoses targeted by California parity legislation. Among those with cooccurring conditions (i.e., dual-diagnosis patients), we examined a model including individual characteristics, treatment services, and extratreatment characteristics to understand CD outcome predictors in this population. We hypothesized that longer CD treatment duration and receiving psychiatric services would predict higher abstinence levels. In particular,patterns of psychiatric services (amount of services, receiving a critical dose, or receiving services concurrently with CD treatment) were assessed in relation to outcome. METHODS: We examined abstinence rates 1 year after intake for 747 adults with and without cooccurring conditions. Among dual-diagnosis patients, logistic regression was used to examine predictors of abstinence. RESULTS: At baseline, dual-diagnosis patients (N=104) had higher levels of medical, family, and employment problems than others. They had similar CD retention and received more psychiatric services during the year after intake and had comparable CD outcomes at 1 year. Length of stay in CD treatment, hours of psychiatric services, number of months with concurrent CD and psychiatric services, and number of 12-step meetings attended were independent predictors of abstinence for dual diagnosis patients. CONCLUSIONS: Chemical dependency outcomes in patients with cooccurring psychiatric conditions were positively associated with the number and patterning of services. Receiving psychiatric services concurrently with CD treatment may be beneficial for dual-diagnosis patients. Future studies should examine how best to integrate services to optimize treatment outcomes.