The analysis of vast statistical data on developed countries and Russia has resulted in estimating the share of R&D expenditures in different branches of industry. Various definitions of science-intensive sector of economy are given. A brief analysis of the world high-tech market helps to understand the most important features of this sector of economy. The necessity to take into account the technological features of science-intensive in formulating science-engineering policy is shown. The estimates of high-tech sector share in the Russian economy and the level of R&D expenditures for different scenarios of development are presented.