We have analyzed the differences in the influence of foreign direct investments on the economic growth of developed and developing countries. We used panel data, namely, the observations for 10 countries during 1983–2013, to construct a model of the dependence of GDP on foreign direct investments for the developed countries. For the model of the GDP as a function of foreign direct investments in the developing countries, we used the observations for 11 countries during 1994–2013. We have reached the conclusion that the influence of foreign direct investments definitely has a positive effect on economic growth in both cases. However, the degree of this influence depends on the type of country. Developing countries get a smaller effect from foreign direct investments due to non-transparent institutional environment and negative influence of other non-economic factors. These findings indicate the institutional and economic environment and, most likely, human capital of the developed countries allow to achieve the full effect of FDI, that is, both capital accumulation and spillover effects. Obstacles reducing the FDI effects, such as insufficient human capital and poor economic and institutional environment, likely exist in the developing countries. Thus, the impact of FDI on economic growth is certainly positive, however the level of this effect depends on the country’s characteristics. This means that the hypothesis that FDI affects developing countries less than developed due to the existence of thresholds in the form of unhealthy institutional and economic environment was confirmed.