ZnO nanowires are recently used in optoelectronic devices such as sensors, solar cells, and light emitting diodes due to its unique optical and electrical properties. In such devices, a contact between the ZnO nanowires and a metal electrode exists. Hence understanding electrical characteristic between the ZnO nanowires and a metal electrode can facilitate optoelectronic device design. In this work, ZnO nanowires were grown on Indium Tin Oxide (ITO) substrates using a hydrothermal method. Simple devices using the nanowires sandwiched between the ITO and a metal contact (i.e. Au, Al) were fabricated and characterized by a current-voltage measurement. Moreover, studies on p-n junctions between the ZnO nanowires and p-type polymers, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and poly(9,9-dioctylfluorene) (PFO), were also fabricated and characterized. The current-voltage measurement of devices clearly shows the rectifying behavior, which is an important characteristic of diodes.