Health Psychology as a discipline is established as an independent field of psychological knowledge, realizing the biopsychosocial approach to health and illness. However there are questions remaining open: how practically this approach is applied in health psychology and what are the borders between health psychology and close disciplines (psychosomatics, body functions regulation psychology, behavioral medicine, positive psychology). The purpose of this paper is to examine the possibilities and limitations in the application of the biopsychosocial approach to health psychology, as well as to compare different alternative sciences based on this approach. There is heterogeneity of biopsychosocial approach revealed, that is based on three different functions this approach has in the regulation of research: the role of ethical and social guidelines, the role of methodological principle, the role of the explanatory model for health and illness. The specificity of the subject area of health psychology implies taking into account issues like wide / narrow definition of the subject in various disciplines; what kind of discipline serves as an integrative; as well as understanding of social situation of science development (including the development of psychosomatic medicine in Russia), its goals and objectives.