Zinc oxide is one of the most promising materials for optoelectronic applications due to its wide band gap of 3.37eV and large exiton binding energy of 60 meV. Zinc oxide nanostructures have wide range of potential applications also in areas such as solar cells, field emission devices, chemical and biological sensors, photocatalysts, light emitting devices, including light emitting diodes, and nano-sized lasers. Preparation of highly structured nanostructures on various substrates is done by chemical spray pyrolysis (CSP) method at moderate deposition temperatures of the substrate (from about 400 to 600°C). CSP is technologically simple deposition technique for manufacturing zinc oxide nanostructures.Flat zinc oxide layers (i.e., as opposed to a layer, comprising nanorods, nanoneedles, nanowires, etc structures) are widely used for electronic and optoelectronic devices, for example, as transparent electrodes in thin film solar cells where simultaneously a high transparency and a low resistivity is required, but also in thin film gas sensors, varistors, and surface acoustic-wave devices.