There is an established ethical and legal duty upon psychiatrists to obtain informed consent before treating a patient, although some exceptions do apply under Mental Health Legislation. The required standard for informed consent has been the subject of important case law in Ireland and other common law jurisdictions and this has caused some uncertainty for clinicians. The standard of informed consent can be viewed from the point of view of what the medical profession thinks is appropriate, or alternatively from the position of what a patient would reasonably expect to be told. These contrasting approaches are discussed in detail. A recent decision of the Irish Supreme Court establishes the ‘patient-centred’ standard for informed consent as the relevant standard in Irish law. The current legal position on informed consent is discussed in relation to common clinical scenarios in psychiatric practice.