The focus of my work is the investigation of stimulated emission in ZnO nanostructures. Currently this material attracts much interest in research and industry since it emits light in the ultraviolet which promises a lot of applications. One kind of examined nanostructures are ZnO nanorods with a hexagonal shape and sizes of 100-300 nm in diameter and several µm length. Due to the high refractive index of ZnO light is strongly confined and therefore the rods form optical resonators. Under pulsed optical excitation the direct gap material provides gain and the rods act as laser, emitting spectrally sharp and amplified light. Secondly also nanocrystalline ZnO powders are investigated with respect to their laser properties. The powder acts in this case as the optically amplifying medium. Simultaneously it causes strong scattering which leads can lead to a feedback of the light. This phenomenon is called random lasing.