Roncus (Parablothrus) pljakici, a new species of cave living pseudoscorpions, is described from the cave ‘Pecina u selu Vrelo’ on Mt. Stara Planina, East Serbia. The problem of its taxonomic position in the subgenus is discussed. The new species is the first representative of Parablothrus to be found in Serbia. It seems possible that R. (P.) pljakici represents an endemic species, specialized for a cavernicolous way of living. The analogies of this and other species of the subgenus point to some similar phenomena which occur in other genera of Balkan false scorpions (Ćurčić 1972). In all these cases, a close relationship among the species inhabiting East Serbia, Macedonia and Herzegovina was noticed. It is probable, therefore, that the three regions represent the autochthonous areas of the original populations of the analysed groups of species, out of which new species came into existence.