Increased knowledge of a species overall habitat requirements is important for enhancing the outcome of any conservation effort. The present study identifies habitat and substrate characteristics associated with high vitality of both core and fringe populations of the suboceanic species Platismatia norvegica. Platismatia norvegica was surveyed at four oceanic sites in central Norway, and at five sites in Sweden situated on the suboceanic fringe of the species' distribution range in Scandinavia. The study has shown that close proximity to watercourses is essential for the occurrence of P. norvegica in suboceanic fringe habitats. Also, results suggest that less acidic bark pH values, especially in combination with close proximity to open water, might be beneficial for the abundance of the species in the suboceanic region, while neither of these factors was of importance for the occurrence of the species in the oceanic core habitats. Also, overall thallus abundances were much higher in the core environments, a pattern which most likely is due to macroclimatic characteristics. While higher bark pH levels in the oceanic region failed to explain the observed differences, there was a good correspondence at site level between abundance and annual wet precipitation. The marginal P. norvegica populations displayed both morphological and distributional responses to the more continental climate. However, close to the watercourses in the suboceanic region, it was found that both thallus abundances and mean values for thallus area surpassed those found in the oceanic region. It is often argued that conservation measures should be concentrated within the distributional core of a species, to achieve an optimal outcome. The present study suggests that, within the zone bordering the streams, conditions for maintaining viable populations of P. norvegica are fully comparable to those in the oceanic region. In view of the scarcity of protected habitats in central Norway, the present study indicates that both set-aside protection and restoration of fringe populations can be of great importance to the conservation of endangered suboceanic lichens in Scandinavia.