Due to isolation, islands are known to harbor a high number of endemics. Although most lichen species are widespread, a number of genera are well-known for the large number of endemics. Often, those endemic taxa have a low population size and are vulnerable to ecosystem change. We carried out a survey of all seven endemic lichens of the island of Porto Santo (Madeira, Portugal, 42 km²) in order to generate data for a IUCN Red List assessment. Six km² of suitable habitat for the species were searched and mapped at 100 m resolution. The main habitat for the species consisted of volcanic outcrops, mainly basalt peaks and lava flows on the slopes. All accessible areas—circa 90% of the peaks and 50% of all outcrops—were surveyed by the authors during one week as a volunteer project. The population size of Anzia centrifuga was estimated to be 50–100 individuals. It occurred only on exposed, stable, vertical, N to W facing rock faces above 240 m, restricting the potential habitat to less than 1.0 km². Ramalina nematodes occurred often abundantly on most of the larger exposed ridges. Ramalina confertula and R. portosantana each occur on several rock outcrops in the N part of the island. Ramalina erosa, R. jamesii and R. timdaliana were restricted to an area often less than 1000 m² in the surroundings of their type localities. After application of the IUCN criteria, all studied endemics fitted well into category Critically Endangered although no immediate threats seem present.