We present a theoretical investigation of the band lineups between crystalline and amorphous silicon, based on the first‐principles pseudopotential method and the model‐solid theory. We find that the offsets are very sensitive to the hydrogen content of the material; the valence‐band offset for a junction with unhydrogenateda‐Si is −0.25 eV, while for hydrogenateda‐Si with a hydrogen content of 11% the offset becomes 0.20 eV. Consequences for the interpretation of experimental data are discussed.