This paper reports findings from a qualitative study concerning the influence of implicit models of mental disorder on shared decision making within community-based mental health teams. One-hundred participants representing five distinct multi-agency groups: psychiatrists, community psychiatric nurses, approved social workers, patients and informal carers operating within Leicestershire, England were interviewed using a standard case vignette describing a person whose behaviour suggests he may have schizophrenia. The results showed that each of the study's multi-agency groups implicitly supports a complex range of model dimensions regarding the nature of schizophrenia, the appropriateness of specific forms of treatment and care, and their respective rights and obligations towards each other. The influence of these implicit model patterns on processes of shared decision making are discussed through evaluating their contribution to our understanding of the power relationships existing between various practitioner groups (including informal carers), and between practitioners and patients during clinical encounters.