Meeting the psychological, social and physical needs of people with cancer is a challenge for individual health practitioners, health administrators and health policy makers. However, there is a considerable gap between recommended best-evidence psychosocial and supportive care and actual practice. This paper provides a discussion of the reasons for this gap using the precede-proceed model as a theoretical framework. The model is a useful way of classifying potential barriers to the application of recommended best practice into three categories: predisposing factors which influence motivation to behave in a particular way, enabling factors which facilitate the enactment of the behaviour and reinforcing factors which increase the likelihood that the behaviour will be maintained over time. Ways of addressing these barriers are proposed and discussed.