Women with serious mental illness (SMI) have disproportionately worse breast cancer profiles than those of other women. The purpose of this project was to examine barriers to and facilitators of breast cancer screening, specifically in formerly homeless women with SMI using the participatory methodology of concept mapping. A series of three concept mapping focus groups were held with 27 women over the age of 40 with a diagnosis of a SMI who live in supportive housing programs, and with 16 housing program staff. Data from the focus groups were combined through multidimensional scaling to create a visual cluster map. Barriers and facilitators to mammography screening generated by the participants clustered into eight categories. Participants rated addressing educational issues as most important and feasible. Interventions designed to improve mammogram screening in this population should address patients' perception of personal risk and should target education and support systems as modifiable factors.