Many studies have demonstrated associations between the distributions and diversities of land molluscs at large scales. We know very little, however, about the importance of factors at small scales and almost nothing about the effects of scale variance. Quantitative sampling of land molluscs and measurement of environmental variables at fine scales allows these effects to be studied. Using this approach it is possible to: (1) assess the effects of environmental variables such as components of habitat structure on diversity across scales and, (2) determine sampling efficacy. Data from locations in southern Iberia show that increased heterogeneity is associated with a higher number of species, but not with higher abundances of species, and that there are significant changes across scales for number of species, abundances and diversity.