The article presents the results of a study of the genre parameters of the preamble to the Constitution of the Russian Federation and preambles to the constitutions of the republics that are part of the Russian Federation. The following aspects are considered as genre parameters (genreforming factors): (a) relevance to the text of a law of a certain sub-genre type. (b) subject matter. (c) communicative functions. (d) subject composition (images of the author, addressor and addressee). (e) spatio-temporal and other circumstantial characteristics.