The controlled synthesis of Cu(OH)(2) nanowires and nanoribbons in a solution phase has been realized with high yield at low cost by simply dropping KOH and ammonia solutions into an aqueous solution of CuSO4 at ambient temperature. It is demonstrated that the morphology of nanostructured Cu(OH)(2) is significantly influenced by the feeding manner of the alkaline solutions. A rational mechanism based on coordination self-assembly and oriented attachment is proposed for the selective formation of the polycrystalline Cu(OH)(2) nanowires and single-crystalline Cu(OH)(2) nanoribbons. In the presence of a polymeric additive, poly(acrylic acid) (PAA), ordered assemblies of Cu(OH)(2) nanorods can be readily obtained. Furthermore, well-defined CuO nanostructures, such as CuO nanoplatelets, nanoleaflets, and nanowires, were produced by thermal dehydration of the as-prepared Cu(OH)(2) nanostructures in solution or in the solid state. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the products.