Objective: To explore how people with dementia, their informal caregivers and their professionals participate in decision making about daycare and to develop a typology of participation trajectories.; Design: A qualitative study with a prospective, multiperspective design, based on 244 semistructured interviews, conducted during three interview rounds over the course of a year. Analysis was by means of content analysis and typology construction.; Setting: Community settings and nursing homes in the Netherlands.; Participants: 19 people with dementia, 36 of their informal caregivers and 38 of their professionals (including nurses, daycare employees and case managers).; Results: The participants' responses related to three critical points in the decision-making trajectory about daycare: (1) the initial positive or negative expectations of daycare; (2) negotiation about trying out daycare by promoting, resisting or attuning to others; and (3) trying daycare, which resulted in positive or negative reactions from people with dementia and led to a decision. The ways in which care networks proceeded through these three critical points resulted in a typology of participation trajectories, including (1) working together positively toward daycare, (2) bringing conflicting perspectives together toward trying daycare and (3) not reaching commitment to try daycare.; Conclusion: Shared decision making with people with dementia is possible and requires and adapted process of decision making. Our results show that initial preferences based on information alone may change when people with dementia experience daycare. It is important to have a try-out period so that people with dementia can experience daycare without having to decide whether to continue it. Whereas shared decision making in general aims at moving from initial preferences to informed preferences, professionals should focus more on moving from initial preferences to experienced preferences for people with dementia. Professionals can play a crucial role in facilitating the possibilities for a try-out period.