Segregation is a relatively new research topic in Finland. Levels of residential segregation are growing, presenting a problem for the welfare state ethos. This thesis investigates how urbanplanning policy deals with the 'problem' of segregation in Finland. The four articles study the interrelationship between the social, the physical, and the perceived city and each dimension's role in the segregation cycle. The first three articles concentrate on the Helsinki metropolitan area, analyzing the social dimension of institutionalized urban policies such as transit-oriented development and social mixing. The last article examines how segregation is recognized in the twenty largest Finnish cities. Perceptions are of interest to urban planning, as they are linked to selective moving patterns, which are one driver of the segregation process. The first article finds interlinkages between neighborhood satisfaction, socioeconomic status, and the share of social housing in neighborhoods. The second article finds differences in neighborhood satisfaction by tenure status, with municipal tenants reporting lower neighborhood satisfaction, quality of life, and perceived safety than homeowners. The second article concludes that while social mixing seems to have bridged the gap in spatial justice among different tenure groups, it has not managed to equalize neighborhood perceptions in the Helsinki metropolitan area.