Introduction: A major challenge in involving people with dementia is to determine what methodology can be used in order to optimally understand, measure, and interpret their needs and wants. The aim of this presentation was to reflect on experiences of assessing needs and wants among people with mild dementia in two user-driven development projects of assistive technology services, the Memory-Lane and COGKNOW projects. Methods and Materials: The user-driven design process in the ongoing MemoryLane project and the finished COGKNOW project followed a sequence of three steps. The first step was to acquire concrete user needs as a base for development, the second step was the development process of prototypes, and the final step the testing and evaluation of final prototypes. In both projects dyads of people with dementia and their informal carers were involved in the assessments. The assessment of concrete needs and wants was based on rigorously developed research questions. In the analysis the different type of data were first analyzed separately for both perspectives, and thereafter integrated to a comprehensive understanding. Results: General abstract questions seemed more difficult to answer for persons with dementia than more detailed and concrete questions. Despite these problems, their answers on general open questions provided valuable additional information to the structured questions. Carers could provide more elaborative information. However, there were more similarities than differences between the answers of the people with dementia and their carers, and few contradictive answers were given. Conclusions: Persons with dementia provide special challenges in user-driven development processes of assistive technology services due to their cognitive impairments. The use of a combination of data collections methods, combining open and structured questions in interviewing persons with dementia and their carers with observations by researchers can provide a comprehensive understanding that addresses some of these challenges.