Sustainable development is a crucial part of a successful city planning. Some scientists suggest urban densification as a method for achieving sustainable cities. In the best of worlds, a perfect balance between ecological, economic and social sustainability would be reached. However, that is rarely the case. Planners must consider the guidelines of planning documents as well as laws, political decisions and stakeholders. These interests can often be conflicting which leaves the planner with tough decisions. Social sustainability can be about achieving equality and healthy environments for all of society. It is therefore important to also include children in city planning. This study aims to examine the planning, which primarily concerns the densification, of the central borough Öst på stan in Umeå. The content, mainly concerning sustainable development, of the comprehensive planning in the municipality of Umeå as well as the planning of a specific quarter which includes dwellings, a preschool and a park, will therefore be described and analyzed. The quarter will also be examined further regarding the actual social sustainability, especially of the children’s environment. Trade-offs, priorities and compromises in planning the quarter will be discussed. In order to achieve the aim of this thesis mainly two research methods, in addition to thorough studying of literature, is being used; primarily planning documents from the municipality and secondly interviews as a complement. The results show that the new quarter is, in many ways, sustainable. The compromises throughout the planning process have however resulted in quite small outdoor spaces which none the least affects children.