Case-Based Reasoning is a methodology that uses information that has been considered as valid in previous situations to solve new problems. That use of the information allows CBR systems to be applied to different fields where the reutilization of past good solutions is a key factor. In this paper some of the most modern applications of the CBR methodology are revised in order to obtain a global vision of the techniques used to develop functional systems. In order to analyze the systems, the four main phases of the CBR cycled are considered as the key elements to organize an application based on CBR.