OBJECTIVE: Previous research has shown that the public have different beliefs to mental health professionals about the helpfulness of interventions for mental disorders. However, it is not known whether the public's beliefs actually influence their behaviour when they develop psychiatric symptoms. METHOD: A postal survey of 3,109 Australian adults was used to assess beliefs about the helpfulness of a broad range of interventions for depression, as well as respondents' current level of anxiety and depression symptoms and any history of treated depression. A follow-up survey of 422 persons who had a high level of symptoms at baseline was conducted 6 months later. These people were asked which interventions they had used to reduce their symptoms. An analysis was carried out to see whether beliefs and other factors at baseline predicted subsequent use of interventions. RESULTS: There were some major discrepancies between the ranking of interventions as likely to be helpful and the ranking of how frequently they were actually used. Interventions involving mental health professionals were often rated as likely to be helpful, but were rarely used in practice. Other simple, cheap and readily available interventions were used the most frequently, but were not the most likely to be rated as helpful. The most consistent predictors across all interventions used were gender, history of treatment, current symptoms and belief in a particular intervention. Of particular interest was the finding that beliefs in the helpfulness of antidepressants predicted their use. However, beliefs were not predictors of use for all interventions. CONCLUSIONS: Beliefs about the helpfulness of an intervention did not always predict actual use of that intervention, although beliefs did predict use of antidepressants. Therefore, campaigns that change public beliefs about effective treatments may also influence actual use of treatments. Interventions preferred by professionals are not frequently used at present. Most people with anxiety and depression symptoms rely primarily on simple self-help interventions, the effectiveness of which has been little researched.