The accurate assessment of occupational functioning is one of the most difficult areas of occupational therapy. There is a strong need for reliable and valid instruments. The translation of measuring instruments is one option, but there are problems that impact on this, e.g. language and meaning, culture, values and social customs. New instruments for occupational therapy should be developed which take into account the sociocultural context. The instrument should be based on clinical needs and should help an occupational therapist to strengthen his/her work in the hospital or the community. The self-evaluation of the activities of daily living for a patient with long-term mental illness (Salo-Chydenius, 1996b) is underpinned by cognitive–behavioural theories. This article looks at the development of an instrument for patient self-evaluation, and evaluates and compares it to standardized English instruments such as Liberman et al (1989), Birchwood and Tarrier (1992) and Bellack et al (1997). This instrument is still at the developmental stage, and further work is required to assess its reliability and validity.