The limiting cause of nanoconfinement of rubber molecules for their selective adsorption onto filler surface has been examined by changing: (1) the void size of carbon black aggregates, (2) the atomic scale roughness and chemical character of carbon black surface, and (3) the kind of filler from carbon black to silica. Nanoconfinement of rubber molecules into carbon black aggregate structure occurs at the concave (similar to 5 nm) formed in between carbon black primary particles. Nanoconfinement is the primary mechanism, whereas chemical interaction between filler and the polymer plays a minor role in the selective adsorption. The new adsorption concept is also examined with silica nanoparticles.