Currently, the radio spectrum is beginning to be crowded due to the rapid growth of wireless technologies this century. However, many studies show that the major licensed bands, such as those allocated for television broadcasting, amateur radio, paging, etc. are underutilized and some of the remaining bands are heavily used. This fact leads to spectrum wastage. Therefore, new techniques are needed to take advantage of the spectrum opportunities causing a reasonable level of interference in the licensed bands. Hence, cognitive radio has become an important research topic in these last years since it tries to take advantage of the unused spectrum by the licensed users. In addition to spectrum sensing algorithms, sharing protocols, policies, among other things, the interference management has become an important topic in cognitive radio in order to manage and fulfil the regulatory constraints. The management of interference is, unquestionably, required to treat and quantify all the interference produced by the unlicensed users at the licensed receivers. In order to manage this interference, the secondary users must be able to adjust their parameters to fulfil these constraints. In the current work is presented an overview of cognitive radio and interference management. Several quantitative and performance criteria are studied as well, in order to illustrate the effect that the different parameters produce on the interference in the licensed bands.