The current situation regarding the euro and the dilemmas „Will the Euro survive the current crisis” opens questions common currency or national currency? In parallel with the process of creating a common currency and the abandonment of national currencies in the European Union, on the Western Balkans unfolded took process abandoning the common currency and variation of national currencies. Both processes offer experience and lessons. Ex Yugoslavia had a common currency the Yugoslav dinar. It was the currency area with over 22 million inhabitants. In the early nineties, countries that have made the dissolution of Yugoslavia, inter alia, monetary sovereigns establish their national currencies and took control of its monetary policy. Dissolution of Yugoslavia was accompanied by leaving Yugoslav dinar as a common currency and the creation of national currencies. In this paper we tested the hypothesis that the existence of national currencies has negative effects on business of the Trans national companies. The theoretical framework is the theory of optimum currency areas (Beyoumi, 1994, Honhan & Lane, 2003, Levin, 2000, Krugman, 2009). The focus is on companies Tondach experience in the Balkans. Period is 2004-2010. The basic method is case method. Research includes the Republic of Slovenia, Croatia, Bosnia and Herzegovina, Serbia, and Macedonia. We used panel 5 x 7 x 5.(Five years, seven countries, five variables: income, investment, exports, imports, exchange rate).