Lepraria impossibilis grows on tree bark, mosses, and soil-covered rocks, occurring in forested and open habitats across South and Central America, including El Salvador, Bolivia, Chile, and Peru, as well as in Iran.

It was found at an elevation of 1,150 m (3,770 ft) in primary forest on the north-facing slope of a ridge, growing on the trunk of a Chaperno (Lonchocarpus) tree.

[2] Another species, L. vouauxii, is similar both morphologically and chemically to L. impossibilis, but can be distinguished by the presence of lecanoric acid.

It has been recorded in forest areas and open habitats across South and Central America, including El Salvador,[3] and has also been reported from Iran.

[3] In South America, where it occurs in Bolivia, Chile and Peru, it grows in high-elevation, open Andean vegetation.