Site-selective deposited ZnO nanowhiskers with semi-circular shape were fabricated on the substrates by a simple two-step approach using an aqueous solution at low-temperature of 100°C. The zinc hydroxide nitrate hydrate prepared by the ultraviolet irradiation was used as a template layer. The forced hydrolysis of a pre-existing template layer in situ at an initial stage in a 200-ml aqueous solution of zinc nitrate hexahydrate-hexamethylenetetramine-polyethylenimine promoted heterogeneous nucleation and growth of ZnO nanowhiskers by site-selective deposition and resulted in the formation of semi-circular shape.