Development activity in Poland is regulated by many legal provisions, but one of the most important acts for the implementation of developers’ projects is the Act of March 27, 2003 on spatial planning and development. The Act includes, among others, procedures for the preparation and scope of local spatial development plans. One of the parameters significant from the point of view of housing development which these plans define is the minimum and maximum intensity of development and the percentage of biologically active space that should be preserved on a property covered by the investment project. The article adopts two research goals. Firstly, it is an attempt to verify, using examples of selected developers, whether they, as profit-oriented entities, decide to develop the property as much as possible or to keep more undeveloped space, which is a more desirable phenomenon from the environmental point of view. Secondly, an attempt will be made to determine how developers in Poland create a biologically active surface in their projects. Based on desk research, it was found that, among the discussed cases, there is no evident tendency to maximize the permissible built-up areas and the created biologically active areas are sparse and not diversified.