'From a democratic theoretical perspective, the vertical limitation of central state power is usually regarded as the main reason for establishing federal order. However, in political reality, this normative principle constitutes only one of several explanations for the processes of decentralization or federalization. The question is, if, and to what extent, the idea of 'vertical separation of powers', has guided recent state reforms in Western Europe. Both centralization and decentralization of a democratic state may be justified by different theoretical objectives. Furthermore, the political salience of relevant arguments depends on contextual preconditions (territorial cleavages, party system congruence, and federal/ unitary form of state). The comparative analysis of respective reform processes in two federal (Germany, Austria), and two unitary cases (Italy, Great Britain), reveals that 'vertical separation of powers', has not been present as a guiding principle, and has not played a key role in these decentralization contexts.' (author's abstract)