Nanotubes of anatase-titania with very high specific surface-area have been synthesized via hydrothermal using the as-received powder of anatase-titania particles, having lower specific surface-area, as a precursor. Various analytical techniques have been used to characterize the as-received powder and hydrothermally processed nanotubes of anatase-titania for their morphology, size, structure, specific surface-area, pore size distribution, photoabsorption, and photoluminescence properties. The dye adsorption and photocatalytic activity of as-received powder and nanotubes of anatase-titania have been studied using the methylene blue as a model catalytic dye agent. It has been shown that, due to higher specific surface-area, the dye removal using the nanotubes of anatase-titania is primarily via surface-adsorption mechanism in the dark; while, that using the anatase-titania particles is via photocatalytic degradation mechanism under ultraviolet-radiation exposure. Hence, the mechanism of dye removal from an aqueous solution using the anatase-titania appears to be highly morphology-dependent.