The main topic of this thesis is the study of various issues related to the synthesis of nitrogen containing nanotubes. This is mainly inspired in the possible applications such structures can have. The practical background lies in the fact that defined n- and p-doping of carbon nanotubes can be achieved by substituting carbon atoms from the tube walls by heteroatoms such as boron or nitrogen (N). This is far from been a triviality because we must keep in mind that if carbon nanotubes are to be used as future building blocks in nanocomposites and nanoelectronic devices, it is imperative to fine tune their wall reactivity, mechanical strength and electronic band gap by controlling the amount of foreign atoms inserted into the tube lattices. Therefore, from an applications standpoint, it is important to be able to carefully control the insertion of different dopants into nanotubes. In this work, a complete picture of the dependence on the combined synthesis parameters is established and a fundamental insight into the formation of N doped nanotubes and other structures (co- products) is provided. As a pioneering idea of this whole work, the use of pure C/N feedstocks in chemical vapor deposition methods is emphasized. With this, it was possible to determine the effects of the reaction atmosphere and the catalyst pretreatment as either favoring or disfavoring agents towards the synthesis of N-doped nanotubes.