Thesis: The use of discretion in public procurement may take place at different stages of the procurement process. The economic literature has widely investigated the benefits and limitations of its use. This dissertation focuses on two dimensions of discretion. First, a public authority has to decide whether to provide a public service in-house or privately. This dissertation empirically investigates the determinants of both remunicipalizations and privatizations for the water distribution services. This decision to switch appears to be mainly driven by economic efficiency reasons. Also, a tendency to switch from one regime to another one in neighboring municipalities influences this decision. Second, this dissertation focuses on public buyer's discretionary power towards the award mechanism. The economic literature acknowledges that even though discretion may yield a better value for money when awarding a contract, it may also facilitate corruption. This dissertation analyzes the impact of investigation for corruption over the degree of buyer's discretion used. As a matter of fact, a municipality investigated for corruption does not react by using less award procedures that allow for discretionary power. Only neighbors of municipalities that are eventually found guilty react, suggesting that responsive neighbors to investigation might also be involved in the case under investigation. Finally, the question of the effect of discretionary power over the likelihood to select a productive supplier is addressed. It follows that an award procedure that allows for discretionary power leads to the selection of less productive firms than an award procedure that does not.