The field of nanocarriers for drug delivery has developed rapidly over the last decades. Recently the innovative approach of self-emulsifying systems has caught researcher's interest. The aim of this study was to investigate influences on cellular uptake of self-nanoemulsifying drug delivery systems (SNEDDS) with regard to droplet size and the presence of anionic surfactants. In order to determine size-dependence, formulations exhibiting different components and ratios were developed. Especially the oil-to-surfactant ratio determined the droplet size of resulting emulsions. Anionic surfactants were dissolved in a formulation by heating and ultrasonics, thereby achieving a maximum of 1 % loading for all chosen excipients. Emulsification was carried out in water, phosphate buffer or culture medium. The resulting nanoemulsions were characterized with regard to particle size, stability and zeta potential using light scattering methods. ^Among the screened formulations, two compositions with three different droplet sizes each were chosen, varying between 35 and 150 nm with a PDI below 0.25. Unloaded SNEDDS of roughly neutral zeta potential (-7 to +3 mV) differed to the increasingly negative value of anionic surfactant loading (-4 to -28 mV). CaCo-2 and HEK-293 cells were chosen as in vitro cell models. A concentration dependent cytotoxicity of nanoemulsions was found on the cells via resazurin assay. Thus 0.05 % SNEDDS in OptiMEM was used for the cellular uptake studies, which were performed on both cell types through incorporation of FDA (1 %) into the formulations. The amount of entered marker molecules was analyzed by fluorescence. These investigations revealed an improved cellular uptake efficiency for some of the incorporated anionic surfactants (up to 1.6-fold), but no tendency regarding droplet size could be observed. ^According to these results, cellular uptake of SNEDDS does generally not depend on the size of the nanoemulsions, but rather the uptake is determined by the choice of components and the amount of surfactants.