This dissertation examines the impact of a semi-presidential system on democratic performance. Does semi-presidentialism encourage institutional cooperation and promote successful democratization, or does it provoke a power struggle, leading to political instability and democratic breakdown? We examine this question in the context of Timor-Leste from 2002-2012. During this time, Timor-Leste experienced a period of cohabitation, divided government and unified majority government. We identify the different levels of institutional conflict during the three periods. We show that there was more conflict under cohabitation than under the other two periods and more conflict under a divided government than under unified majority government. This work provides qualified support for some of the hypotheses associated with semi-presidentialism.