It's shown that the transformation process is put by national experts in a quite similar chronological frame, mostly as 1989/90-1992; 1992-1994/95; 1995-1998/99; 1999, in view of the contents and coverage of the national science & technology policy. However, approaches to the transformation system varied depending on (i) specifics of national S&T systems during the socialist period, (ii) the approach to the transformation process, focusing either on following the Western model or on a series of measures meant to 'preserve' the institutional build-up of the S&T inherited from the past. But in spite of these distinctions, the transformation process in post-socialist countries of CEE ended up by adopting the conceptual documents harmonized with ones existing at the EU level. However, as the analysis shows, in early 2000s the national S&T system in its narrow sense, that is, R&D / innovation performers, nevertheless remained at the first phase of the transformation process, in the condition of isolation/fragmentation, in a major part of the CEE countries. Therefore, national science & technology systems could be conceptualized by early 2000s, but, for the most part of post-socialist countries, failed to be realized. The problems of fragmentation can be better understood through (i) evaluation of the institutional change within the national science & technology system, which reveals the most difficult segment in the transformation process, 'branch' science; (ii) analysis of supply and demand concepts in the context of national S&T systems.