Terrestrial moliusc faunas are described from 38 semi-natural, deciduous woodlands in the geographically variable area of the South Pennines, England. The same number of species (44) is recorded from woodlands on limestone and from those on millstone grit-shales, but 20 and 12 species are significantly more frequent in these two geological categories respectively. Many of the limestone and gritstone/shale species can be classified as calcicoles and hygrophiles respectively. Faunas from the limestone sites are relatively homogeneous but those from millstone grit/shale woods are very variable, both within and between sites. These differences appear to be related to levels of habitat diversity and especially to the occurrence of marshy areas. Several geographical groupings are tentatively identified among the limestone sites. The affinities of the sites with similar woodlands elsewhere in the British Isles, and the conservation significance of the fauna, are discussed.