The advance directive (AD) is an important resource in oncology and all areas of medicine directly involved in the care of palliative patients. It provides people with the right to have their living wills honoured when they cannot respond by themselves. Despite their importance, ADs are still underused in most countries due to multiple factors. The objective of this review is to better categorise the barriers and difficulties that could impair the composition and implementation of ADs, allowing direct efforts against these obstacles. After the literature review, we believe that there would be five steps in the trajectory of an AD (discussion, composition, registration, access and implementation) and that all those steps can be affected by factors involving the health systems and professionals, the patient themselves and relatives or caregivers.