The issue of institutional design of competition authorities has attracted increasing interest since the early 2000 but requires further elaboration. This article attempts to fill some gaps by providing a general framework to examine a number of dimensions of this issue under three headings: the goals, the functions and the organization of competition authorities. While there is no unique institutional design which would fit all countries, a number trade-offs should be considered in designing a competition authority. These trade-offs may lead to different designs across countries depending on the local conditions. Ultimately choosing the best possible design for the competition authority given the local conditions is crucial to ensure that the competition authority is most effectively able to discharge its duties.