Surfaces coated with ZnO nanorods have the potential to be used as photocatalysts in flow type reactors. The prerequisite for their use is the mechanical and chemical stability of the nanorods under flow conditions. The effect of the thickness of the seed film on the stability of the ZnO nanorod arrays grown on the seed layer by hydrothermal method is investigated in this work. In addition, the viability of its use in photocatalytic flow type reactors is also assessed under flow conditions. The thickness of the seed film deposited by sol/gel method was varied in the range of 40 nm 650 nm. Verticality of the nanorods, found to be the most effective parameter in the dissolution of the rods, is related to the seed layer characteristics. Preliminary experiments showed that degradation activity of the nanorod films in photocatalytic reactors also depends on the seed layer thickness through the verticality of the rods attained. Excellent verticality and highest crystallinity could be obtained in this work with nanorods averaging 4 mu m in height, grown on 220 nm-340 nm thick seed layers. Good correlations for verticality of nanorods could be obtained with X-ray diffraction results when the seed layer is characterized by the average skewness and kurtosis of the roughness. Morphology and the structure of the seed films and the nanorod arrays are characterized by field emission scanning electron microscopy, atomic force microscopy and X-ray diffraction. The optical properties of the films are determined by photoluminescence and ultraviolet spectroscopy measurements. (C) 2014 Elsevier B.V. All rights reserved.