The surfaces of the wet-etched and activated glass substrates were first seeded by a simple dip-coating method using the zinc acetate precursor solutions with and without polyvinyl alcohol (PVA). Then, the substrates with two kinds of freshly prepared seed layers (i.e. with and without PVA) were annealed at 250 and 400 °C. Seed-mediated growth of rod-like zinc oxide (ZnO) nanostructure arrays by a chemical bath deposition was carried out as the second step in the formation of continuous ZnO films. PVA, which was added to the seed precursor solution, increased the vertical alignment of the ZnO nanorods along the c-axis. This was confirmed by the appearance of the strong (002) X-ray diffraction peak and by the cross-sectional scanning electron microscope (SEM) images of the films. Even though the well-aligned nanorods were synthesized on the PVA-modified seed layer, they exhibited poor photocatalytic activities in the degradation of C.I. Acid Red 88 azo dye compared with the more randomly aligned ones. The color removal efficiencies of the “random” nanorods (i.e. without PVA modification) under ultraviolet A light illumination were nearly two times higher than those of the well-aligned nanorods.