  In this paper, the general features of the neutrino sector in TeV scale
quantum gravity theories, such as ADD and Many Species Theory, is investigated.
This class of theories has an inherent way to generate small neutrino masses.
After reviewing this mechanism it is generalized to a realistic three-flavour
case. Furthermore, a procedure is presented how to diagonalize a mass matrix
which is generated by this class of theories and how one can find the Standard
Model flavour eigenstates. The developed general approach is applied to two
specific scenarios within ADD and Many Species Theory and possible effects on
neutrino oscillations and on unitarity of the lepton mixing matrix are
calculated. Finally, a short overview of phenomenology which can be potentially
testable by the nowadays neutrino experiments is presented.

High Energy Physics - Phenomenology