One of the most fascinating experimental results in the fabrication of artificial nanostructures is the creation of a macroscopically ordered superlattice of Ce adatoms on Ag(111) [F. Silly et al, Phys. Rev. Let. 92, 016101 (2004)]. Here, performing kinetic Monte Carlo simulations, we study the formation of Ce superlattices at the atomic scale. It is demonstrated that the surface-state mediated long-range interaction between Ce adatoms can lead to their self-assembly into a well ordered structure. The temperature of the substrate and the concentration of Ce adatoms are shown to play a key role in this process.