Abstract Mining operations disturb the natural hydrological cycle at a local scale by creating new pathways for water flow and conveying large amounts of water, both for use in ore beneficiation and through the dewatering of mining workings. Sulfide minerals exposed to water and oxygen are oxidized through chemical and microbial-enhanced reactions, significantly altering the quality of water (acid mine drainage). Stable isotopes may reveal important information concerning water origin and transfer, as well as chemical processes and solute fluxes within the aqueous environment. Several case studies illustrate the use of stable isotope techniques for clarifying aspects related to water circulation in mining areas within Romania and Finland. Hydrogen and oxygen stable isotopes coupled with total dissolved solids have been used to characterize mine water and for assessing water sources, flow paths and mixing processes at some Romanian mining sites. At Talvivaara mine in Finland, water isotopes and chemical composition were used to determine the extent of waste water contamination in groundwater systems after a leakage at gypsum ponds.