Geothermal water can be found under the surface of the Earth and it is a natural source of heat and energy, which has been used since ancient days especifically because of its healing effect, a convenient temperature and convinient geographical position. Thermal water springs differ in a temperature, a chemical composition of water, an aquifer type and their way of usage. The balneological analyses of the examined water of Lipik show that it is mineral, fluorine, sodium- hydrogencarbonate- chloride hypertherm and for this reason it is used for a balneotherapy and a physical therapy. In order to explain the appearance of the Lipik geothermal water, it is necessary to know the geological structure of the surroundings of the water spring. In order to determine the origin of the geotermal water, fundamental geological, geochemical and isotopic methods are used. Thanks to the geological research in particular we find out that in the area around Lipik reverse or overthrust relations are present. The Lipik geothermal water is the highest mineralized water in the area of Northern Croatia based on its chemical composition, most likely because it is a mixture of meteoroic, connate and maybe juvenile water. Geochemical and isotopic research studies show that the geothermal water of Lipik is poligenetic in origin, which coincides with a highly complex geological structure.