[2] It occurs in southeastern Australia and New Zealand, where it grows as an epiphyte in temperate rainforest environments.

It inhabits cool temperate and warm-temperate rainforests, where it typically grows as an epiphyte on tree trunks, branches, and twigs.

[3] In New Zealand, common host trees include Melicytus ramiflorus and Beilschmiedia tawa.

[3] Although Radula demissa is yet to receive a formal conservation assessment, it was assigned a provisional status of "Not Threatened" in 2021.

Additionally, genetic studies have revealed reciprocally monophyletic geographic clades between New Zealand and Tasmanian populations, suggesting limited gene flow across the Tasman Sea.