Introduction. The role of firm in the conditions of information economy is investigated in the article. Modern economic realities reflect the global change of economic paradigm and the transition to the information society. This fact naturally influences on behavior of firm as active economic agent. Considering theoretical aspect of a traditional role of firm as a main manufacturer in economy, there is topical issue: whether there is this role invariable in the conditions of new realities of information economy? Theoretical analysis. The author made his own hypothesis that in post-industrial economy than the bigger number of firms is formed and the more effectively they work, the more steadily and more intensively there is a GDP growth. The graphic modeling based on the extensive empirical data containing information on the number of firms and change of an indicator of GDP in five leading countries (the USA, China, Japan, Germany, France), which have made transition to information economy confirms a hypothesis. Further the attention of the author has been concentrated on the analysis of information sector of economy, because information sector is the leading making sector in post-industrial economy. As a result of the analysis the revealed earlier author’s hypothesis has received confirmation again. Results. The author makes a conclusion that the firm is the main making subject of information sector in particular and all information economy in general and there is direct link between indicators of number of operating companies of information sector of economy and GDP. Growth of one indicator involves growth of another. It means that firms of information sector give an essential contribution to the general welfare.