The aim of the thesis is to explore socially shared ideas about mental illness in everyday contexts. Drawing on social representation theory, organizations for users of mental health services and self-help groups are regarded as communities where social knowledge is constructed that makes intersubjective understanding of illness experiences possible. In order to investigate such knowledge as a resource in joint construction of meaning, a theoretical model is introduced where a distinction is made between a discursive level of situated ‘representational work’ and an underlying level of sociocultural resources. A focus group study was carried out with 27 participants who label their health problems as anxiety, depression or bipolar disorder, and were members of service user organizations. The focus group conversations were analysed with regard to thematic, interactional and discursive features to answer the questions: 1) how is mental illness represented, 2) how is the mentally ill person represented, and 3) how are others’ views on mental illness represented. The results show how mental illness is represented as a complex phenomenon that is contextualised to a number of frames of reference. Further, the analysis identified different types of resources that are utilized in representational work: local knowledge of the communities, medical concepts, different explanatory models, narrative structures, metaphors and conceptual dichotomies. It also revealed dialogical properties of the representational work that have rhetorical functions for self-presentation as a team performance. The discussion suggests that widely shared resources are put to use in group- and situation-specific representational projects, and that representations that are produced in group discourse can be characterised as ‘polemical social representations’ that respond to a double stigma of mental illness in everyday life where mental illness is regarded as a sign of ‘weakness’ as well as ‘otherness’.