With the collapse of the communist regimes, the post-socialist countries are facing the problem of building new legal and institutional systems which will adequately address the needs of the markets. They also try to implement new reforms. But the transition towards economic and market reforms across the bloc has been very uneven, producing the countries-winners, countries-laggards, and countries-losers. There have been some attempts to explain that unevenness from the temporal path dependency perspective and from geographic proximity perspective. Can we explain this unevenness better drawing upon the theory of institutional isomorphism? This paper is not ambitious and built exclusively on literature review. It attempts to borrow from some middle-range social theories of institution building and, especially, the theory of institutional isomorphism by DiMaggio and Powell. It shows that some parts of the bloc seem to be surprisingly isomorphic. The paper suggests an explanation of the possible causes and applicability of the phenomenon of isomorphism in the post-Soviet bloc. In particular, it: 1) contrasts the facts of the transformation with the theory of institutional and organizational isomorphism, 2) makes a fair causal comparison with other explanations, 3) claims the adequate causal depth for the explanation, 4) points at an adequate causal mechanism of the transformation.