La Vallée-Poussin spent many years in Rome, where he was admitted to the Maltese order with the rank of "Cavalier Donato" (i.e. not of noble lineage, but given for services rendered to the order) and where he became a member of the Academy of Arcadia. On his return to France, he was in 1789 admitted to the Académie de Peinture, with a tableau de réception entitled Return of the young Tobias and his meeting his mother and father. He died in Paris.
