We present a systematic study of the leading twist structure functions of the deuteron, We find that the nonrelativistic and relativistic calculations are qualitatively very much alike. However, three main features systematically distinguish a consistent relativistic approach from the nonrelativistic one: (i) the binding effects are larger, (ii) the effect of Fermi motion at high x is stronger and (iii) the relativistic description of the structure functions b D 1,2 is fully consistent, unlike the nonrelativistic approach, which is internally inconsistent and violates the fundamental sum rules.