Sovereign Wealth Funds (SWF) are nowadays one of the main institutional global investors. Their assets exceed the total assets of hedging funds and private equity funds. They operate globally, in both portfolio investments and direct investments. The dynamic development of these funds raises numerous questions about their impact on the economy, also in the context of combating effects of the financial crisis. The main objective of the article is to present the trends that can be observed on the SWF market over the last years, related to both the development of the funds and the transparency of their activity. The number of SWF and the value of their assets have been increasing, as well as their investment activity. The transparency of their operations has been also growing, however this market still remains not very transparent. It is also sometimes believed that sovereign wealth funds can be driven by political reasons (for instance attempts to take over a controlling interest in companies of strategic importance for beneficiaries of an investment) rather than by economic reasons.