This thesis examines the existing Danish research of social mix as a planning instrument. On the basis of seven Danish studies the first analysis examines the understanding, the expectations and the effects of social mix. The results, and in particular the lack of evidence on the effects of social mix is then incorporated into the following analysis. Through interviews with eight representatives from municipalities and non-profit housing organizations it is examined why they aspire to implement social mix in their deprived housing areas. The following analysis concludes that aspiring to achieve social mix is based on a desire to attract socioeconomically advanced residents and to create socially mixed cities. These aspirations are based on political ambitions of not wanting residential areas to be segregated and represented on the ghetto-list, and it is expected that social mix is part of the solution.