The taxonomy of lichen species morphologically similar to Thelidium auruntii and T. incavatum in Finland is being revised. Based on ITS and morphology, ten species occur in Finland. All species are restricted to calcareous rocks. The Thelidium auruntii morphocomplex includes six species: T. auruntii, T. huuskonenii sp. nov., T. pseudoauruntii sp. nov., T. sallaense sp. nov, T. toskalharjiense sp. nov. and T. sp. 1. In the ITS phylogeny, T. auruntii, T. pseudoauruntii and T. sallaense group 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. The Thelidium incavatum morphocomplex includes four species: T. declivum sp. nov., T. incavatum, T. mendax sp. nov. and T. sp. 2. This morphogroup is not resolved as monophyletic in the ITS phylogeny, with only T. declivum and T. mendax forming a strongly supported group. Thelidium incavatum is rather common in SW Finland, with one separate locality in eastern Finland. Thelidium declivum occurs only in the Oulanka area. Thelidium mendax occurs in the Oulanka area, but one locality is known from eastern central Finland. Thelidium sp. 2 is known from one locality in SW Lapland. Keywords: Calcareous rocks, DNA barcoding, ITS, lichenized fungi, new species, phylogeny.