Recently there has been a great interest in the study of La2NiO4 due to its MIEC properties, which make it suitable in electrochemical devices, such as cathode in ITSOFCs, permeation membranes or gas sensors. This work is focused on the study, from a fundamental point of view, of epitaxial c-axis oriented La2NiO4 thin films deposited by PI-MOCVD on different substrates, to achieve a better comprehension of the microstructural characteristics, their variation with strain and their influence in the high temperature transport properties. Moreover, the epitaxiality permits the measurement of the films' properties in two perpendicular directions, a direct inset of the anisotropy. La2NiO4 is the n=1 member of the Lan+1NinO3n+1 Ruddlesden-Popper family. We have also attempted to deposit c-axis oriented films of the n=2, 3 and ? members and studied the variation of their transport properties with n. The techniques and results presented in this book will result very useful to a wide range of researchers working in the fields of oxide thin films, K2NiF4-type compounds, fundamental study of transport properties in oxides and solids in general and in the possible applications of the material.