There is an increased interest in supporting persons with dementia with technical services in daily life. The aim of this case study was to explore the complex issues involved in the process from a user driven development to the acceptance and usage of a new digital assistive device for persons with mild dementia. Even though it was developed in a user driven process and personalized to meet their individual needs they rarely used it. To deepening the understanding of this disparity between actual usage and perceived usefulness, the participants were studied whilst performing daily life activities through participant observations and interviews. Their partners were interviewed two years after the first observations to clarify the change in needs over time. The results show that the participant needs encompassed occupation, safety, social interaction, and memory support together with the receipt of general support. The overriding requirement for both participants was a need to maintain their self-image. When the digital assistive device did not correspond with the participants' expectations or view of themselves, their interest in using it faded, since the digital assistive device failed to support their self-image. The acceptance of a digital assistive device by a person with dementia is a process that begins with identifying and personalizing the functions of the device according to individual needs, and then supporting the usage and the gradual integration of the device into daily life. During this process, the person's self-image must be taken into consideration and supported.