The structures and optical properties of ZnO nanowire and nanotube are investigated by ab initio calculations of the pseudopotential density functional method. It is found that the imaginary part of dielectric functions of the ZnO nanowire and nanotube have different peaks with respect to light polarization. Compared to the ZnO bulk, the corresponding peaks of dielectric functions of ZnO nanowire and nanotube are blueshifted. Both dielectric function spectrums and loss function spectrums of ZnO nanowire and nanotube show the moderate optical anisotropy with respect to light polarization. (C) 2007 Elsevier B.V. All rights reserved.