The International Classification of Functioning, Disability and Health (ICF, WHO 2001) made a great advancement over ICIDH of 1980 in the understanding of the human functioning and disability. However, in both of them there is an important 'missing' element. That is the subjective dimension of functioning and disability. One of the authors (S. Ueda) published on this topic in 1981 both in Japanese and English. It had originated from his clinical experience in rehabilitation medicine. The understanding of the inner world of the client has proved a great asset in clinical practice. This paper explains its importance and provides a definition. It also proposes a tentative framework of a classification of subjective dimension of functioning and disability as the starting point for more intensive and extensive discussion on this important problem, and for its future inclusion into ICF.