Anodized tubular $TiO_2$ electrodes (ATTEs) with three noticeably different lengths are prepared to determine their optimum length for the photo-driven activity in the reaction of Cr(VI) reduction and hydrogen evolution. The ATTEs with ethylene glycol have longer $TiO_2$ tubes (7-15.6 ${mu}m$) than those with hydrfluoric acid (0.6-0.8 ${mu}m$). These samples, which differ only in the length of the tubes, with a wall thickness of ca. 20 nm, consist mainly of an anatase crystalline phase after heat treatment at $650^{circ}C$, since the anatase crystallites at the tube walls do not undergo transformation into rutile phase, due to the constraints imposed by the wall thickness. Among them, the medium size (ca. 8 ${mu}m$) tubes provide the optimum conditions, irrespective of the light intensity, which is explained in terms of the correlation between the amount of photons and the adsorbed electron acceptors and their location. Photocatalytic Cr(VI) reduction leads to ca. 60% reduction of Cr(VI) even under 1 sun irradiation with the medium-sized anodized $TiO_2$ tubes, but only ca. 20% with the short- and long-sized tubes. For hydrogen evolution, tubes longer than 8 ${mu}m$ do not exhibit better performance with any light intensity.