Documentation in early childhood education and care (ECEC) institutions has been developed for decades in various contexts. Today, documentation is preferred as an inclusive method of evaluating, planning, and developing ECEC in the curricula of many countries. Qualitative research on documentation has increased in past years, but quantitative research on the connections between documentation and ECEC practice has remained behind. We will present a study in which a total of 2889 children, 194 kindergartens and preschools, and 179 teams of ECEC educators in 13 municipalities in Finland participated. On the basis of our quantitative analysis, we argue that documentation is inherently connected with child-centred and carefully planned ECEC practices and the children's participation, well-being, and ability to learn. One of our main findings is that documentation is not yet fully exploited in the Finnish ECEC. As a result, we encourage ECEC officers and educators to develop documentation further. (author abstract)