The study contains projections of the economic development, over the period of 40 years (from 2000 until 2040), for 22 high-income OECD countries and 22 Central and Eastern European economies. The projections are based on the endogenous growth theory that allows for capturing both phenomena of the knowledge-base growth in the high-income OECD countries, and the real convergence process in the catching-up countries of Central and Eastern Europe. Obviously, any projection made for the period of 40 years is subject to a great uncertainty and forecasting error. Over the period of 40 years deep and unpredictable changes may take place in the direction of the technological progress, political situation and social stability of nations, international flows of production factors, and institutional development. Nevertheless, three scenarios presented in this study show the plausible range of the GDP growth that may be expected, given the best knowledge available today.