This article discusses the appropriate dispersant for titania (TiO2) nanopowder in organic-based suspensions. Four types of oleyl-based dispersants, namely, oleyl alcohol, oleic acid, oleylamine, and oleyl phosphate, which have the functional groups hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), and phosphorous [-P(=O)(OH)(2)], respectively, were compared for their ability to disperse TiO2. Experimental results for zeta potential, adsorption, FT-IR spectroscopy, and rheology, as well as theoretical calculations, indicate that dispersants with -P(=O)(OH)(2) and -NH2 were more efficient than those with -COOH or -OH. The primary reason for this difference is related to the different interactions of TiO2 with various dispersants and to different dispersion mechanisms. In addition to the major functional groups, -OH in the chemical structure of dispersants was important, as it might have other effects such as destabilization of the suspensions.