The extent of illicit substance use within inpatient mental health settings is becoming a major cause of concern. This poses growing challenges not only for the management of inpatient units, but also for providing continuity of care. Service users with co-occurring substance use are more likely to disengage from services. The process of engagement can be hindered by negative attitudes of staff. This study aimed to identify and explore multidisciplinary staff attitudes and experiences in caring for inpatients with co-occurring ill-mental health problems and illicit substance use. A questionnaire incorporating the Drug and Drugs Problems Perceptions Questionnaire (DDPPQ) was used with a non-probability sample of 84 multidisciplinary staff working on nine mental health units. Semi-structured interviews were then carried out with 10 members of staff. Overall, respondents reported: lack of training; difficulty in accessing support structures; and problematic issues with multidisciplinary decision making and processes. The DDPPQ results showed that staff who had received training held less negative attitudes towards illicit substance users regardless of their length of clinical work experience or type of work setting. Recommendations are made about the importance of training and staff support for the development of less negative attitudes towards this client group. © 2010 Blackwell Publishing.