This dissertation is structured into 3 essays in which I analyze the economic effects of regulation and liberalization of hydrothermal systems. So far empirical and theoretical studies about power markets have been done mainly for thermal systems, in which equilibrium conditions reflect the fact that current production decisions can be analyzed separately from future production decisions. In hydrothermal systems, however, strategies are dynamically connected what yields equilibrium conditions different from thermal systems. This difference in the nature of the equilibrium is the main building block upon which I will analyze some important questions like liberalization of the market, investment, market power of generators and policies towards its mitigation and to compare the effectiveness of some common proposed policy interventions recommended to thermal systems in the context of a hydrothermal system. In the first essay, I analyze one of the main concerns in restructured electricity markets: the market power of generators. I show that two common mitigation measures proposed for thermal power markets (incentives to long- term contracting and horizontal deconcentration) do not necessarily affect the firms` market power in hydrothermal systems in the same way as in thermal systems. In the second essay, I consider the incentives to investment in the Brazilian centralized dispatch in which future entry of new capacity is one of the most important determinants in the optimal management of the system. When investment is not determinative, investors can choose the most appropriate time to enter into the market. Previous real option models incorporates this flexibility on the optimal time to invest but do not consider that each potential new firm may affect the current optimal stock of water to be left to the next period. The fact that indicative entry plan does not take into account that investors` choice of the optimal time to invest may affect current values (especially the stock of water to be left to the next period)and hence reinforcing possible distortions in the investment decision, given future prices and dispatched quantities depend on the current optimal dispatch. In the third essay, I discuss the restructuring experiences of Brazil and California. Despite different goals and different initial market structures, both undertook the restructuring of their respective electricity sectors largely based on the same deregulation framework in vogue in the 1990s. Coincidently, a few years later, both were facing serious crisis in their respective electricity sectors. The lack of attention to some important aspects of the liberalization or deregulation of the electricity sector and inadequate regulatory incentives could have exacerbated rather than attenuated the deleterious effects of their respective crisis. The main lesson from both experiences is that liberalization or deregulation of electricity markets should be carefully implemented, with special attention to the potential impact of the new structure on the equilibrium allocation during market stress situations.