Abstract: This thesis analyzes two economic problems using network theory. In the first paper, we analyze the hold-up problem in outsourcing industries. Typically, in automobiles, semiconductors and software, companies and suppliers of inputs jointly invest in specific assets before making transactions. We investigate how the structure of these relationships generates a large number of trading oportunities, equates the bargaining power of firms and reduces oportunistic behaviour. The second paper analyzes the ináuence of the structure of interactions in self-organized teams (academics, law, accounting, sports) on individual levels of effort. Because these teams do not have a principal, we study the way in which the agents organize tasks and roles to achieve higher levels of production.