Abstract : This paper discusses two grammatical formatives which encode a potential meaning when added to a resultative compound : DE in Standard Mandarin (which comes from the verb 'get'), and LIAO/LAO in some non-standard Northern Mandarin dialects. Both forms also show a perfectivizing function in other environments. The potential suffix LIAO was never discussed before in the literature, whereas DE and its historical development are a much studied topic. We analyze the link between their potential (modal) value and their perfective (aspectual) value, including the hypothesis of a possible haplology to account for potential V-de or V-liao forms.