ABSTRACT: Fatra mineral water is distinctly of the Na-HCO3 chemical type (A1 = 78 – 82 equiv. %) with a high CO2 content. The high ratio of rMg/rCa exceeds 1, and this is very interesting because it is quite atypical for Western Carpathian mineral waters. With regard to its chemical type, while chloride concentrations are low, sulphate concentrations usually vary between 150 and 400 mg·l-1. Moreover, large quantities of ammonium ions (22 – 79 mg·l-1) and boric acid (14 to 27 mg·l-1) are also found in this mineral water. The unique water chemical composition is formed in a small hydro-geological structure with low flow and low yield from the BJ-2 a BJ-4 borehole resources. The Mann-Kendall trend analysis test indicated the declining character of almost all the selected chemical components. This downward trend is due to the reduction in content of all components while maintaining the original Na-HCO3 chemical type. The conceptual model presents a summary of geological, hydrogeological and hydro-geochemical data currently compiled. This is supported by precise information on the chemical and isotopic composition of the water and on the palaeo-hydrogeological development of this area. The conceptual model interprets the genesis of this mineral water and thus stresses the importance of its quantitative and qualitative protection.