The adsorption of anionic and nonionic polydisperse surfactants was studied by ellipsometry on titania and silica, respectively. The effect of polydispersity is mainly observable in the low concentration range. In the case of polyethoxylated nonionic surfactant adsorption on silica, the long chain components are preferentially adsorbed at low concentration. Ethoxy-sulfated surfactants do not adsorb on silica in the same conditions (pH > 3). Their ethoxy chains seem to have no interaction with the titania surface at pH 2.5 where adsorption is mainly due to an electrostatic interaction between sulfate head and positive sites of the surface. At saturation, surface concentrations and thicknesses of the adsorbed layer lead to the same interpretations as those deduced from results obtained on powders with the same surfactants or on flat surfaces with monodisperse surfactants : the surface seems to be covered with aggregates of limited extension whose thickness is comparable to micelle diameter. It is also worth noticing that the linear evolution of apparent areas per molecule with ethoxy number is very similar for nonionic and anionic sets.