﻿AbstractThe taxonomy of lichen species morphologically similar toThelidiumauruntiiandT.incavatumin Finland is being revised. Based on ITS and morphology, ten species occur in Finland. All species are restricted to calcareous rocks. TheThelidiumauruntiimorphocomplex includes six species:T.auruntii,T.huuskoneniisp. nov.,T.pseudoauruntiisp. nov.,T.sallaensesp. nov,T.toskalharjiensesp. nov.andT.sp. 1. In the ITS phylogeny,T.auruntii,T.pseudoauruntiiandT.sallaensegroup together, but the remaining species are placed outside of this clade. All the species have northern distribution in Finland, occurring on fells in NW Finland and/or in gorges in the Oulanka area in NE Finland. TheThelidiumincavatummorphocomplex includes four species:T.declivumsp. nov.,T.incavatum,T.mendaxsp. nov.andT.sp. 2. This morphogroup is not resolved as monophyletic in the ITS phylogeny, with onlyT.declivumandT.mendaxforming a strongly supported group.Thelidiumincavatumis rather common in SW Finland, with one separate locality in eastern Finland.Thelidiumdeclivumoccurs only in the Oulanka area.Thelidiummendaxoccurs in the Oulanka area, but one locality is known from eastern central Finland.Thelidiumsp. 2 is known from one locality in SW Lapland.