Occupational therapy focus on client-centred, occupational performance intervention may become complicated by the phenomena of self-awareness. The problem of awareness deficits in clients with neurological disorders may be attributed to neurological impairment of self-awareness and/or psychological denial of disability. These phenomena present themselves more commonly in combination than dichotomously and have implications for treatment outcomes. Individuals with impaired self-awareness or denial face difficulties with motivation and participation in therapy, and the adoption of compensatory strategies, which ultimately impacts on rehabilitation outcome. The extent of unawareness versus denial can be assessed by observation of a client's behavior and this information can be very useful in directing the treatment approach. The purpose of this paper is, therefore, to discuss the phenomenon of unawareness and/or denial of disability and its importance to successful rehabilitation outcomes, current thinking and research conducted in different countries. Also, detailed case examples of three clients representing three major populations of traumatic brain injury, stroke and schizophrenia who may exhibit unawareness and/or denial of disability will be presented, including intervention strategies for both phenomena.