The chapter analyses some of the informations about the first generations of Norman dukes given by Ademar of Chabannes in his Chronicle, which had been often considered as spurious or doubtful. It first gives an outline of Ademar’s career and the composition of his work in order to clarify the changes and additions made by him across versions of his chronicle and to shed light on his sources, influences and intentions. Several passages were reworked, sometimes substantially, in ways that bring up questions about the information Ademar had at his disposal and how he used it in the fabric of his narrative. Despite a bad reputation, one can see author’s efforts to bring coherence and credibility to his narrative, to amend his text as new information reached him and to create a credible version of the beginnings of Norman history. The chapter explores what kind of information he was given at different stages of the composition of the chronicle, and examines possibilities of identifying persons who possibly may have help him to modify his version of the Norman past.