Although　private　information　retrieval　and　oblivious　transfer　are　equivalent　in　classical　cryptography,　we　show　that　the　existence　of　secure　quantum　private　information　retrieval　is　necessary　but　not　sufficient　for　secure　quantum　oblivious　transfer,　Which　provides　a　strong　evidence　of　nonequivalence　of　two　flavors　of　oblivious　transfer　at　the　quantum　level.　(C)　2015　Elsevier　GmbH.　All　rights　reserved.