Constant population growth in urban areas is one of the main global problems, and its importance grows with the depletion of non-renewable resources. The efficient, effective and responsible use of land is supposed to be an aim, the achievement of which will profit cities. The crucial question is, how cities can achieve this aim. The author of this article intends to discuss the individual problems which prevent achieving an appropriate density in Warsaw, and find ways of solving or reducing these problems. A proposed main hypothesis is, that the introduction of an alternative type of housing, namely co-housing can become a way to obtain a good density in the cities. Confirmation of this hypothesis is derived on the basis of the analysis of residential estates created following the rules of co-housing developed in Germany, in relation to similar problems. The purpose of the article was also to remind that Warsaw has a rich tradition in creating social efforts developments. The main social ideas was presented on the basic of the project of Polish housing estate designed in the Rakowiec district in Warsaw by H. and Sz. Syrkus, which was established in 1934-1938 The research part of the article was conducted through a comparison of spatial elements of Warsaw, employing the same criteria, which were adopted based on the several, selected characteristics of good density published in the ULI report, such as: mixed use of land, planned, cohesive, liveable, spacious, flexibility, design, green. The conducted comparison demonstrates, that Warsaw has a lot of different problems with obtaining a good density. These are: mono-functional areas in the suburbs, social disparity, the housing market dominated by developers, lack of enough, well-arranged public spaces combined with residential areas, lack of identity neighborhoods, insufficient attention to the local context in the process of designing new buildings, insufficient attention to the environment in terms of creation of buildings, too little green spaces and gardens in the inner city. The presented analyses show that the introducing concept of co-housing can help Warsaw with obtaining a good density. In order to obtain a high quality of the urban space, decisions regarding it should therefore be made simultaneously on three scales: spatial planning, urban planning and architectural planning. Architecture must cooperate with the existing urban fabric. All users of urban life should participate in its creation: development companies, municipal authorities that are responsible for spatial order, architects and residents.