Innovations have become the most important factor of growth and competitiveness in the modern economic paradigm. The innovative model or development type dominates today as a milestone of national, regional and corporate strategies. Intensive diffusion of innovations (DI) is the most important precondition for innovative economy functioning. The essence and theoretical foundations of DI research have been presented in the article. Attention is drawn to the fact that DI is a special type of communication and social process. The types (non-commercial transfer, commercial transfer, free diffusion), subjects, factors and preconditions of DI, as well as its functions in the economy have been distinguished. The state participation in favorable conditions providing for the flow of DI is defined. The primary focus was on the analysis of DI in the ICT sector. In this regard, the objects of DI are identified and the connection with digital economy formation, including its various manifestations, is substantiated. The digital economy structure, the digital innovation phenomenon and software features as the basis of ICT that all sectors of the economy depend on in the era of informatization, are presented. An analytical frame for the study of DI in the ICT sector is proposed; this includes: innovation characteristics; subjects characteristics; innovative ICT diffusion process characteristics; ICT diffusion features characteristics in certain economy sectors where they are used; the diffusion environment characteristics; the characteristics of the forms of DI. Attention is drawn to the role of education in DI that makes it possible to overcome its knowledge-related barriers. The main approaches to the study of DI in the ICT sector (macro-, meso-, microanalytical, cognitive, organizational, social, market, institutional approaches, etc.) are proposed. The directions of a quantitative assessment of the DI processes and consequences in the ICT sector are highlighted. The intensity of DI is commensurate of the innovative activity level and the innovative processes effectiveness (symmetry), as well as with a unified understanding of innovation. The areas that need to be addressed in the framework of the DI analysis, in order to solve the problems of its development and the efficiency improvement of enterprise participation, including marketing of innovations have been defined in the presented material.