According to the new tendency of planning and developing mental health services in response to the individual needs, many tools assessing needs of persons with mental disorders were created during last few years. This paper presents some of them, with concentration on the Camberwell Assessment of Need Short Appraisal Schedule (CANSAS). The aim of CANSAS is to identify patient's needs, thus the tool can be a part of routine clinical practice and research, as well as a component of service evaluation. Because "need" is a subjective concept, CANSAS incorporates separately the views of both users and staff about needs. The tool was developed in the Institute of Psychiatry King's College in London and is now successfully used in many countries all over the world. It has been also translated into Polish and used in the first Polish studies on the needs of persons with mental disorders.