Following the institutional part of the economic transition and the legal/political involvement in European integration process, the Central and Eastern European countries (CEEC) must promote their innovation capacity and competitiveness through innovative processes and products to attain the real transition. This article analyses fiscal measures with the intention to disclose tax incentives design of three CEEC being or not being EU Member States - Slovenia, Slovakia and Belarus. The authors research whether three small open transitional economies pay enough attention to enhancing innovation by tax measures. The results of comparative analyses have shown that three CEEC have chosen different approaches and models to improve the tax treatment of Research, Development and Innovation (RDI). The differences are essential.