Silicon nanowires have emerged as a cheap and efficient technology for nanostructured Si necessary for electronic devices as well as anode material in Li battery technology. They are typically grown via the vapor-liquid-solid mechanism and gold nanoparticles at the catalyst side. Here we compare the CVD growth of those silicon nanowires on different substrates, namely Si with native SiO₂ as well on a carbon surface. The presence of carbon does change the typical characteristics of single crystalline growth to more amorphous or polycrystalline growth regardless of different process conditions typically varied to get optimal nanowire growth.