This article is a service report based on the experience of the Combined Psychosis and Substance Use Programme (COMPASS), which aims to provide integrated treatment for people who experience coexisting mental health and substance use problems. A fundamental role of the service is to deliver a structured training package based on a Cognitive-Behavioural Integrated Treatment approach to staff within mental health services. We aimed to establish whether the needs of staff prior to training were consistent across various service areas and whether our training package can enhance staff confidence and skills to work with this client group. The final aim was to consider if confidence and skills can be maintained over an extended period of time. This article is based on service evaluation data collected between the late 1990s and 2011. Data that had been collected from staff across diverse service areas within a large Mental Health Trust in the UK were analysed. There was a high degree of consistency across the service areas. Prior to training staff expressed interest in combined psychosis and substance use problems and felt that it was part of their role to work with this client group. However they also reported that their knowledge of and competence in the area could be improved. Following the receipt of training staff confidence significantly increased and remained high at our most recent follow up 10 years later. The different strands of evidence provide robust support for the aims of our work. Specifically the significant role of training and continued support and supervision in increasing the confidence and skills of mental health staff responding to combined mental health and substance use problems.