Presidential power and constitutional issues are at the very core of recent popular upheavals in the former Soviet republics, as demonstrated by the Orange Revolution in Ukraine in 2004, and similar protests in Georgia in 2003 and in Kyrgyzstan in 2005. After the demise of the Soviet Union, these countries opted for a particular form of semi-presidentialism, here referred to as president-parliamentary. This dissertation deals with president-parliamentary systems, as well as with the other form of semi-presidentialism, namely premier-presidentialism. The study examines a typical feature of semi-presidentialism, i.e. intra-executive conflicts between the president and the prime minister/cabinet, by analysing the pattern, institutional triggers, and implications of such conflicts in Central and Eastern Europe. In addition, the choice of semi-presidentialism and differences in transitional context and constitutional building are accounted for. The following countries are specifically dealt with: Bulgaria, Croatia, Lithuania, Moldova, Poland, and Romania, Russia and Ukraine. The study’s empirical base is a mixture of data derived from literature, reports, review of constitutional documents, as well as from an expert survey conducted among analysts with an expert knowledge on the countries under scrutiny. The results suggest that both actor-oriented and historical-institutional factors have to be considered in order to understand why so many post-communist countries ended up with semi-presidentialism, and why there is such a sharp divide between Central Europe and the (non-Baltic) former Soviet republics with regard to the choice of semi-presidential type. The pattern of intra-executive struggles reveals that conflicts were somewhat more recurrent in the early period following the transition, but persist as a frequently occurring phenomenon throughout the post-communist period. The most common type of conflict has revolved around division of powers within the executive branch. As for triggers of conflict, the study suggests that certain institutional factors, such as electoral concurrence and party system fragmentation, have been important. Regarding the management of conflict, and the options available to the conflicting parties, the analysis indicates that the constitutional courts have played an important role as conflict mediators, and that attempts of changing the constitution, and using public addresses are options preferred by the presidents. Finally, the analysis shows that intra-executive conflict is associated with cabinet instability. A case study example also illustrates how the president-parliamentary framework can be related to policy ineffectiveness. The study finally concludes that premier-presidential systems have great governance potential provided that the party systems develop and consolidate. The conclusions regarding the president-parliamentary system are less encouraging, and it is argued that the adoption of this system is an important factor in relation to the failed democratisation in many post-Soviet countries.