The thermal conductivity of amorphous/crystalline silicon superlattices and crystalline core/amorphous shell silicon nanowires is calculated with molecular dynamics simulations. The thermal conductivity of the superlattices is of its periodicity and takes values close to the bulk amorphous one. For the case of amorphous/crystalline Si nanowires, we studied a specific configuration where the core is crystalline and the shell is amorphous. The thermal conductivity of such nanowires is very close to the amorphous one. Finally, we compare the results for silicon and germanium nanowires.