Sciaridae (Diptera) from forest and mire habitats from three localities in central Finland were identified. The material consisted of 609 specimens belonging to 106 species. The following species were found as new to Finland: Bradysia subbetuleti, B. submoesta, B. subscabricornis, Corynoptera fera, C. furcifera, C. saetistyla, C. subsedula, Cratyna spiculosa, Leptosciariella helvetica, Lycoriella micria, Pseudolycoriella brunnea, P. nodulosa, Scatopsciara neglecta, Trichosia glabra and Sciara sp. n. (Menzel & Salmela, in prep.) and Ctenosciara exigua sp. n. The latter is described as new to science. Bradysia subbetuleti, Leptosciariella atricha, Leptosciariella tuberculigera and Lycoriella micria are redescribed. The occurrence of some rare or poorly known species is discussed, and the importance of peatlands for sciarid biodiversity in the boreal region is emphasized.