The composition of Web Services has been a topic of vital interest for supporting the tasks of both electronic commerce and the integration of applications among different firms by means of the web. The aim of this paper is to present an analysis about how the planning techniques in Artificial Intelligence can be used to carry out the composition of web services. This paper describes the main solutions outlined so far under this approach and the current problems for carrying out a true automatic composition, problems which become challenges still to be solved in this line of research.