The paper presents the analysis of spatial suburbanization using a multi-indicator method. Based on features related to geodetic areas (according to the directions of their use) such as built-up areas, urbanised lands, arable lands, residential, recreation and leisure areas, road transport areas as well agricultural and forest areas transformed into local land development plans - six suburbanization indicators were developed. After the standardisation of such indicators, a summary index was obtained making it possible to determine the suburbanization degree. The validation of the proposed method was made by comparing individual municipalities with the unit type determined using the Webb method. The analysis made it clear that the only four units with spatial features of the city lying in the proximity of Warsaw, for which Polish capital could be enlarged are: Piastów, Pruszków, Marki, Józefów and possibly Sulejówek.