The study found that drug-treatment clients with anxiety or depression (common psychological problems) had low levels of understanding of clinical terminology for co-occurring drug and mental-health problems, except for those clients who had read relevant literature or had participated in programs developed by drug-user organizations. The service-provider interviews recognized the low levels of consumer mental-health terminology and advocated a client-centered approach that avoids the use of clinical terminology. The authors, on the other hand, advise that drug-treatment providers should encourage clients to discuss mental-health problems and not avoid using clinical terminology, since that may undermine the development of mental-health literacy among clients. Treatment services could benefit from working with drug-user organizations in the development of resources that could improve awareness and understanding of mental-health problems among drug-treatment clients. The interviews were part of an Australian qualitative study of barriers and incentives to drug treatment for people with both illicit drug and mental-health problems. Participants were recruited from Brisbane (Queensland), Perth (Western Australia), and Sydney and Bathurst (New South Wales). Client interviews were semistructured, focusing on drug-use history, experiences of drug treatment, mental-health background, and experiences of mental-health treatment. Staff who worked with clients with comorbid drug and mental-health problems or who had responsibility for comorbidity-related services were identified and interviewed. The semistructured interviews focused on the providers’ experiences in working with people with drug and mental-health problems, the ways in which their services addressed comorbidity, and barriers and incentives to drug treatment for people with common mental-health problems. 43 references