Based on the tight-binding model, we investigate the formation process of quantum dots onto graphene nanoribbons (GNRs) by the sequential adsorption of hydrogen atoms onto the ribbon's surface. We define the difference between hydrogenation processes onto the surface of zigzag (ZGNR) and armchair graphene nanoribbons (AGNR) by calculating the binding energies with respect to the energy of isolated hydrogen atoms for all considered structures.