Modern media space is constantly enlarged by new media texts, which have various social, cultural, informative and organizing functions. This process in Russia has its feature - a very high speed of development and " overtaking character" of the process. Many texts and speech genres of European and American media space are loaned, but the principles of building such texts are not understood by authors in full. Very often exact copying of the external form of any kind of text causes detriment of its content because of the misunderstanding of the organized internal notional structure and the lack of the due analysis of such kind of text as a speech phenomenon. Problems of this kind occur in the speech genre of social advertisement (SGSA). Due to historical circumstances this genre appeared in Russian speech 20 years ago and quickly became demanded. The frequency of the appearance of social advertisement texts in the media space of the country demonstrates the essential need for SGSA on the part of the society. SGSA should be studied from the linguistic point of view - it will help to better understand the principles of its functioning and conditions under which this genre can be a communicative success. The aim of the work is to compare 3 main parameters of SGSA - namely its communicative purpose, the author's image and the addressee's image. The material for the analysis includes more than 100 texts of Russian and English social advertisements. The comparative analysis is considered to be most efficient, because this genre has existed in the English language much longer and is used much more often. It can help to some extent to predict the development of SGSA in Russian. On the other hand, the comparative analysis gives an opportunity to find out the originality of SGSA in the Russian language and its national features. The comparative analysis shows the variability of the genre presents more exactly the borders of its speech realization, describes the diversity of its dictum content. The result of the work is the classification of SGSA messages based on the degree of detalization of the addressee's image. The classification includes 3 basic types of SGSA messages: with "vague", "detailed" or "personified" addressee's image. Similarity and differences in the realization of other genre parameters (such as the author's image, communicative purposes and dictum content) are defined in the work as well. The communicative purpose of the SGSA is usually more distinct in English than in Russian. Perlocutionary effect desired by the author is always rather obvious in the English advertisement. Differences in the realization of the paradigm " author's image - addressee's image" condition the perception of the genre by the society. In the domestic media space SGSA messages are usually perceived as instructive, while in English practice the typical genre project in the addressees' mind is closer to the realization of the idea of spreading knowledge. In Russian the most popular themes are smoking, alcohol and traffic violations. In English the spectrum of SGSA themes is much wider: adoption, rejection of genetically modified foods, popularization of local foods with the aim of decreasing pressure on ecology while transporting, the Internet behaviour, domestic violence, tolerance to sexual minorities, and so on. The differences in the realization of the genre main parameters in 2 linguistic cultures and the greater frequency of the use of the "personified" and "detailed" addressee's images in SGSA in English help to better understand the factors influencing the communicative success or failure of SGSA messages in Russian.