Oxygen (δ18Os) and stable carbon (δ13Cs) isotopic compositions of modern terrestrial gastropod shells from Lipari Island, in the Aeolian Archipelago (Sicily), have been analysed and compared with local meteoric water δ18O (δ18Op) and vegetation δ13C (δ13Cv) respectively. Results reveal that the δ18Os–δ18Op relationship over the study area differs from those obtained on continental Europe and Italian shells, implying that even at the scale of the Mediterranean basin different relationships may co-exist. These differences have been interpreted as the increasing influence of Mediterranean vapour water on Tyrrhenian coasts at relatively low altitude (up to ~ 600 m asl), which compensates for the effect of the δ18Op, and possibly of temperature, on shell δ18O. The steady-state flux balance model (FBM), in agreement with previous studies, suggests that snails are active prevalently at night. Shell carbon isotope ratios reflect the δ13Cv, as predicted by the metabolic model and represent a valuable tool for identifying C3 plants with very distinct isotopic signatures.