This document specifies a classification of the imperfections likely to be generated during an additive manufacturing operation by PBF-LB (laser beam powder bed fusion) or PBF-EB (electron beam powder bed fusion) for metal parts. This document also indicates the most probable causes of the formation of imperfections and gives some illustrations taken from feedback. NOTE This classification applies to both PBF-LB and PBF-EB processes and can be extended to other additive manufacturing processes.