The paper is grounded in the idea that a theory of mobile media, like that of any other scientific discourse, must be built on solid conceptual and taxonomical bases. Within this context the paper brings together previous fragmented approaches to studying mobile media, analyses them, and develops a set of definitions and classifications of contents and applications in order to consolidate the construction of a robust mobile media theory. The paper finishes with a reflection on the ongoing mutations of this field and their implications, suggesting that scholars need to rethink the basic concepts behind their theories.