ABSTRACT: BACKGROUND: In order to support evidence-based policies for reduction of stigma, a better understanding of its components: ignorance (knowledge), prejudice (attitude) and discrimination (behaviour) is necessary. This study explores public perceptions and quantifies stigma for three chronic mental disorders: autism, schizophrenia and bipolar disorders in France. METHODS: Survey of 1000 adults selected from an established market research panel. The 21-item questionnaire explored knowledge, attitudes and behaviours toward each disorder. RESULTS: Although 95% respondents recognized the names of each disorder fewer than 70% could report specific characteristics and only 33% considered that publically available information was adequate; most respondents identified the media as their main resource. Labeling of conditions in a negative way was frequent (61%) when referring to mental disorders in general, but fell significantly (18%) when linked to an individual with a disorder. Individuals with schizophrenia are assumed to be dangerous; 65% respondents would engage in social distancing from such an individual, versus 29% for bipolar disorders and 7% for autism (p < 0.001). In contrast to other disorders, discrimination against schizophrenia was only partly attenuated in those with familiarity with mental disorders (through personal or family illness). CONCLUSION: This first population-based survey in France shows that attitudes towards bipolar disorders and autism are less prejudicial than towards schizophrenia. However, most public attitudes and behaviours towards different disorders appear to be based on assumptions rather than knowledge or evidence suggesting a generic information or anti-stigma programme is unlikely to be effective.