This study investigates the definitions of the construct "young children in need of special support" given by preschool staff in Sweden in 540 preschool units. The study has a mixed-methods design based on qualitative analysis of an open-ended question and quantitative analysis of questionnaire responses. The results reveal two general perspectives in definitions of the construct, a child perspective and an organisational perspective. Units with a child perspective had a higher proportion of children in need of special support, especially girls. The study highlights that the term "children in need of special support" is partially socially constructed and is partially based on perceived child characteristics. The perceptions of what is considered to be a child in need of special support held by staff in a unit may impact on the services provided to children in need of special support. (Contains 2 tables.)