In recent years, there has been a growing recognition of the fact that organizations acting alone rarely succeed in tackling complex social problems. The result is the emergence of a new approach, collective impact, which has shown promising results in the US, among other other countries. SFI will evaluate the impact of two projects that employ this approach for the first time in Denmark. The projects are aimed at narrowing the social gap with respect to loneliness and and obesity among children in the two Danish municipalities of Lejre and Helsingør, respectively. Both projects are part of an initiative titled “Narrowing the social gap – testing a new ambitious approach to increased well-being among vulnerable children in two municipalities”, launched in collaboration by Socialt Udviklingscenter SUS, Helsefonden and the two municipalities. The projects are scheduled to run from 2016 to 2028.