The development of assistive technologies has an important impact on the user's activities of daily living and social participation. However, assistive technology identifies persons with disabilities. In this paper, the psychological effects of using a mobility aid were considered before forming the concept of a new device. To identify detrimental factors, a qualitative research approach was adopted in a study on 12 older persons. The investigation revealed that older persons had a dilemma in using mobility aids between maintaining body functions and extending mobility activities. In addition, there are two sides to the dilemma, the function and the image of the body. The process to assuage these dilemmas was clarified and a psychological model was built up. The generation process of the psychological conflict obtained from qualitative data was revealed by modeling details and taking movement, body function and body appearance into consideration. Development of useful assistive technology will be improved by taking account of compositive observational study on the body, the life and the psychological situation of older persons.