The present invention relates to new nalmefene salts which salts fall within at least one of the two following categories: non-hydrate forming salts and non-solvate forming salts. In particular, the invention relates to the hydrogen adipate salt, the hydrogen malonate salt, the lactate salt, the hydrogen fumarate salt, the hydrogen succinate salt, the benzene sulfonate salt, the hydrogen maleate salt and the salicylate salt of nalmefene. The present invention also relates to such salts for use in therapy.