ZnO nano/microstructures are grown on Si(111) substrates using two types of thermal evaporation set-up. The effects of thermal evaporation set-up conditions and substrate temperature on the morphological and optical properties of ZnO nano/microstructures are investigated. Tubes with either one-end open and one end sealed (OOE), or both ends open (TOE) are used as the objects that could change the conditions in a thermal evaporation set-up. Observations show that, under similar source and substrate temperatures, such changes result in different shapes and sizes of ZnO structures. Room temperature photoluminescence (PL) and Raman spectroscopy (RS) studies demonstrate that the ZnO structures grown in the OOE tube have better crystalline quality and optical properties than those grown in the TOE tube. In fact, the results show that the morphology and crystalline qualities of the products can be controlled by the set-up conditions.