The article studies the status of French clé ’key‘ and Dutch sleutel ‘key’ which are recurrent in complex nouns such as mot-clé / sleutelwoord ‘keyword’, notion-clé / sleutelbegrip ‘key notion’ and figure-clé / sleutelfiguur ‘key figurè. In spite of the semantic similarities between the two elements, both occurring in similar compound-like constructions, it is shown that the degree of cohesion of N-clé and sleutel-N widely differs. More particularly, whereas sleutel forms cohesive NN compounds, clé can be observed in adjectival contexts, in the same way as its English counterpart key (e.g. un rôle absolument clé ‘an absolutely key rolè’, ce livre est absolument clé ‘this book is absolutely key’, etc.). This paradox is dealt with within the theoretical framework of Construction Grammar.