The present paper provides new estimates of the impact of investment in R&D on long-term economic growth. In particular, we estimate a dynamic empirical growth model using panel data for OECD countries from 1970 to 2004. This study is the first to investigate whether the specialization of R&D activities (i.e. share of R&D investment in the high-tech sector) has an additional effect on GDP per working age population. Using a system GMM estimator in order to control for endogeneity, we find that both the ratio of business enterprises' R&D expenditures to GDP and the share of R&D investment in the high-tech sector have strong positive effects on GDP per capita and GDP per hour worked in the long term. (C) 2007 University of Venice. Published by Elsevier Ltd. All rights reserved.