Adsorption of cationic surfactants (dodecyltrimethylammonium bromide, 1RQ; 1,2-bis(dodecyldimethylammonio)ethane dibromide, 2RenQ) has been investigated on titanium dioxide with a dodecyl chain anchor. The adsorbed amounts of 1RQ and 2RenQ increase with increasing concentration of the dodecyl chain anchor on,titanium dioxide, where the adsorbed amounts of 1RQ at saturation are considerably greater than those of 2RenQ. Changes in the dispersion stabilities and the zeta potentials of the titanium dioxide suspensions are well correlated with the adsorption behaviors of the surfactants. The adsolubilized amounts of 2-naphthol in the surfactant-adsorbed layer also increase with increasing concentration of the dodecyl chain anchor for 1RQ and 2RenQ, whereas those with 2RenQ are greater than those with 1RQ even though there is a smaller amount of adsorbed 2RenQ. These differences in the adsolubilization are attribued to the surfactant compactness in the adsorbed layer estimated by ESR.