Recent advances in fabrication technologies of metallic nanostructures have opened a new branch of nanophotonics. Those structures show significantly different behaviour compared to the mi- crowave regime due to the negative refraction index of noble metals at optical frequencies. Popular applications are for example light harvesting, cancer therapy, molecule sensoring, light guid- ing, higher harmonic generation, and enhanced spontaneous emission. However, since many effects take place in the evanescent near field, special measurement techniques are required in order to investigate those structures. This work is dedicated to the numerical modeling of electron beam based microscopy techniques like Electron Energy Loss Spectroscopy (EELS) and Cathodoluminescence (CL).