The area of cannabis and psychosis has received considerable academic and media attention over recent years. Current research has explored reasons for use and investigated possible 'causal' pathways. These studies have tended to focus on questionnaire-based or quantitative methodologies, with less emphasis on the qualitative accounts of people with psychotic experiences that use cannabis. This thesis aims to address the absence of qualitative research by applying a grounded theory methodology to the area of cannabis use and psychosis. The researcher recruited eight participants with psychotic experiences, four of whom regularly used cannabis and four of whom had regularly used cannabis in the past. Initial research questions focused on the reasons for participants' cannabis use and their understanding of the relationship between cannabis use and their psychotic experiences. Participants were found to have both positive and negative experiences of cannabis use. Participants spoke about different ideas with regards to the relationship between cannabis use and psychotic experiences, including there being no link, it being a catalyst, there being a multifaceted relationship and cannabis having caused psychotic experiences. During the course the research an additional area of interest arose relating to participants' experiences of nondisclosure or openness of cannabis use with health professionals. This was followed-up and investigated. The findings of the research are compared to the available literature and implications for clinical practice are discussed, as are the methodological issues of the study. On the basis of this research, it is suggested that health professionals, academics and the media may want to think about cannabis and psychosis in a more nuanced manner.