Decentralisation has been justified as a tool for democratic improvement and political stability, an instrument to improve efficiency, a means of managing heterogeneous societies or a guarantee for territorial and social cohesion. However, sometimes the practice of decentralisation leads to mismanagement, corruption, clientelism and lack of policy coherence, among other negative side effects. What is essential to decentralisation is not the transfer of functions and resources from higher to lower levels of government, but the relationship of interdependence between them in the sense that each level can, to some extent, condition the functioning of the others. The reasons to decentralise can be political or technical, and its development can result in opportunities and threats, benefits and risks.