The lichen vegetation associated with calcareous rocks, areas of long snow-lie and the margins of high-level lakes in North Wales is described. It includes Porpidia ochrolemma (Vain.) Brodo & R. Sant. and Rhizocarpon anaperum (Vain.) Vain, new to the British Isles, plus a further 30 taxa recorded for the first time from Wales. The relative importance of the montane lichen vegetation of North Wales is assessed by comparison with areas in other parts of the British Isles. It is shown to exceed in interest any montane area in England or Ireland but to be below the standard of an otherwise comparable area in Scotland.