The aim of the paper is to examine the experiences of the euro zone functioning over the last few years. The authoress is considering the importance and effectiveness of using the convergence criteria in preparing the EU countries for participation in the euro zone.She then moves on to institutional and legal solutions concerning a single monetary policy in the euro zone and decentralized budget policy of the member states. In particular, she analyses the practical functioning of solutions disciplining a budget policy as included in the Pact of Stability and Rise. The conducted research indicates that the public finance regulations have not been able to efficiently reduce too high budget deficits. The new member states of the EU preparing for entering the euro zone should immediately start the reform of their public finance which would enable them to reduce the risk of too high budget deficits that might arise after replacing their national currencies with the euro.