The indiscriminate use of lying, when communicating with patients with dementia, is questioned in terms of ethics and acceptability. In this article we present the concept of "therapeutic lying", to describe those situations where a "non-truth" is used in the patient's interest and not that of the healthcare professional. The debate is still open, so it is necessary to better clarify risks and benefits of lying in the context of care, both to safeguard patients and to allow healthcare professionals to respect ethical and moral standards.