Problematic substance use (PSU) affects 39.5 million people worldwide, an increase of 45% in the past decade. Homelessness is a chronic and growing issue, affecting approximately 100 million people globally. The bi-directional relationship between PSU and homelessness, including the inhibition of housing acquisition via PSU and of difficulties maintaining sobriety through homelessness, is well-established. Cognitive research has identified numerous traits which may be trained to optimise PSU recovery; of these, time perspective, affectivity, and self-control appear central. Meanwhile, a body of work documents executive function disparities between individuals with and without homes. However, despite the high co-occurrence between PSU and homelessness, the implications of these for PSU recovery appear considerably unexplored. The major hypothesis underlying this body of research is that cognitive adaptations associated with homelessness increase risk of PSU. The traits Desire for Control, Locus of Control, Affective Forecasting, and Recent Life Events were investigated. Firstly, this project aimed to delineate the relationship between Locus of Control and abstinence in PSU treatment clients. Secondly, to reveal potential differences in cognitive traits relative to stable and independent accommodation. Thirdly, to investigate possible variance in the role of these traits for sobriety in PSU treatment clients, dependent on residential stability. Finally, to examine the potential ability of a simple intervention to adjust relevant traits and substance use in people experiencing homelessness. A systematic review examined the role of Locus of Control in PSU treatment client recovery. Cognitive assessments and residential histories of 60 adult PSU treatment clients were compared and independently correlated with treatment outcomes. Efficacy of an episodic future thinking intervention via Internality was investigated with people experiencing homelessness in detoxification treatment. Our major findings indicate that moderated Locus of Control and particularly Internal Locus of Control beliefs may best facilitate optimal PSU treatment outcomes, irrespective of housing status. This trait may also be modifiable using a brief cognitive reframing intervention with people experiencing homelessness in detoxification treatment. Significant differences between homeless and housed groups on selected cognitive variables were not revealed. Future research and practice should consider the potential impact of homelessness on cognitive traits pertinent to PSU treatment.