From an editorial point of view, the list of books included in the Hebrew Bible and in the Christian Bible demonstrates big differences in terms of name, way they are grouped together, order and number of books. This is valid not only for the Catholic and Orthodox Bibles which add in their canon of the Old Testament the writings which are not included in the Hebrew Bible, but also for the Protestant Bible. How to explain these differences? Is it only a simple editorial choice or is it a characteristic of the Christian canon of the Old Testament? To answer these questions, we intend to present a critical investigation of the Masoretic Text and its Greek version, the Septuagint, which takes into consideration the main “differences” about the titles, groups, order and number of books.