Our article focuses on the problem of greenery management in urban areas in terms of the spatial form of greenery as well as biologically active areas. Due to the importance of the spatial form of greenery in shaping the positive features of the city’s local climate, the authors have proposed a method for assessing the spatial form of greenery (MASFoG), which is an extension of the existing and widely used method. In addition to the inventory of plants, the spatial model has been created (the 3D model rendered in the geographic information system, GIS), which is a novelty for the method. The method allows for visualizing and calculating the spatial form of greenery – the real biologically active size of the studied area, as well as to estimate real losses in the environment resulting from the introduction of planned changes, e.g., cutting down greenery because of construction of new facilities. The method may facilitate management of the city’s greenery, especially in planning and spatial development: (1) at the stage of drawing up the planning documents and (2) at the stage of specific investments before taking the final decision concerning their location and activities related to natural compensation.