The 2015 UK Supreme Court judgment in Montgomery v Lanarkshire reinforces the importance of informed consent to medical treatment. This paper suggests that Montgomery recognises the challenge faced by vulnerable individuals in choosing between treatment options and making decisions with appreciation of information about material risks. The judgment endorses a form of weak paternalism to safeguard such persons, which is not disrespectful of the aggregate principles of the Mental Capacity Act 2005. But ethical practice requires professionals to tread carefully between weak and hard paternalism in the context of therapeutic interactions with vulnerable patients, while ensuring their awareness of material risks.