Nanowires with different nitrogen concentrations were grown by Metal-Organic Chemical Vapor Deposition (MOCVD) using DEZn, N2O and NH3as zinc, oxygen and nitrogen doping sources respectively. Low temperature photoluminescence, Raman spectroscopy and Transmission Electron Microscopy are combined to study the incorporation of nitrogen in the wires. The observation of donor-acceptor pair band confirms that the incorporation nitrogen in ZnO nanowires is responsible for the creation of acceptor centers. The additional peaks observed in Raman are correlated to nano-sized inter-atomic distance fluctuations observed in TEM. These domains combined with a resonance effect are probably the explanation of the huge Raman cross section observed for the impurity related peaks.