An important stage in the CIS countries integration process intensification is the Customs Union (CU) formation as part of the EurAsEC, consisting of Belarus, Kazakhstan and Russia at first, with a further accession to this Union of other EurAsEC participants when ready. The main advantage of the Customs Union is the arrangement of conditions for a free movement of goods and citizens of the three states, the investment cooperation activation, common projects implementation. Still, the formation of the Union also holds definite risks for Kazakhstan. These risks and problems challenging all CU countries are investigated in the article, and it is concluded that in the course of the Union formation serious results have been achieved, but the partner states should move in a stepwise manner towards a Common Economic space creation.