The paper approaches the study of the thesis genre from a functional and structural perspective. The aim of this research is to identify communicative purposes and to describe the superstructure of linguistics and philosophy thesis, written by undergraduate and master students. The methodology consisted in the application of existing, as well emergent categories to a corpus made up of 20 theses collected from the TFGPUCV-2010 Corpus (5 theses from each discipline and level). According to the findings, there are differences regarding the superstructure depending on the discipline. In respect to the communicative purposes there differences between discipline and level can be observed. The explicitness of the communicative purpose of each section of the superstructure varies. According to our results, we conclude that the thesis genre is not homogeneous and varies according to the disciplines more than the academic degree, responding to the necessities of particular discourse communities.