Quantitative easing operations (QE) carried out during the last ten years by world central banks have become a reaction to the weakness of traditional instruments used to counteract the financial crisis of 2007-2009 and the following recession. This article reviews the peculiar features of QE, theoretical explanations of their influence on economic situation and the evidences of their efficiency as an instrument of monetary policy. The author concludes that QE exerted a considerable impact on financial markets processes but they were much less successful in reaching macroeconomic goals of monetary policy.