Cognitive impairment is prevalent among people with substance problems and a factor affecting retention in treatment. Empirical phenomenography was used to systematically explore how people with cognitive impairment viewed a novel residential rehabilitation program - Project RE PIN - designed with cognitive compensatory behaviour change activities and from a strengths-based approach. Twelve participants took part in semi-structured interviews and cross-case analysis identified the overarching theme of change. Key program elements were the safe environment, structured routines, modified psycho-educational material and staff support. Critical changes that participants attributed to the program were in dealing with their own and others' emotions, experiencing daily life without drugs or alcohol and reframing their self-view. Fear and anxiety about relapse were common and few participants had strategies or support to cope in the future. This study demonstrates that program activities changed participants' thoughts, feelings and behaviours about themselves and their substance use. The results indicate that RE-PIN's modified content and processes can benefit people with cognitive impairments in treatment. The study highlights that some treatment users may be vulnerable to resumption of drug use despite gains made during a residential program and their desire to remain substance-free.