OBJECTIVE: The development of the Antidepressant Compliance Questionnaire (ADCQ), assessing patients' attitudes and beliefs on depression and antidepressants. METHOD: A 51-item questionnaire was applied to 85 psychiatric out-patients with a DSM-IV diagnosis of major depressive disorder (MDD). This data set was used to assess psychometric properties of the ADCQ. The questionnaire was also applied to 272 primary care out-patients with MDD. RESULTS: A principal component analysis revealed four dimensions with good internal consistency and acceptable test-retest reliability: 'perceived doctor-patient relationship', 'preserved autonomy', 'positive beliefs on antidepressants' and 'partner agreement', resulting in a final questionnaire comprising 33-items. Responses were independent from depression severity and patient age. The response patterns of both psychiatric and primary care patients are provided and illustrate the many erroneous beliefs on antidepressants. CONCLUSION: The ADCQ has good psychometric properties; further investigation should investigate whether this questionnaire is predictive of patient compliance.