An annotated check-list of the bryophytes of the Montseny massif (northeastern Iberian Peninsula) is presented, based on literature and herbarium records revision as well as collections made by the authors. A total of 352 taxa were recorded, out of which three were hornworts, 80 liverworts and 269 mosses. Intensive surveys of original locations of threatened, extinct and protected species in the massif were carried out. Species whose local populations became extinct were those with a strong preference for wet and oligotrophic habitats, such habitats have been severely damaged in recent decades. We discuss possible strategies for effective conservation of those bryophytes whose local population have suffered a decline, like targeted legistation and establishing specific protected areas.