ABSTRACT: Findings from research into the Ďurkov hydro-geothermal structure have significantly contributed to the knowledge of geothermal structures in Slovakia, where its geothermal and hydrogeochemical conditions are unique. The following findings were noted; (1) the highest temperature of geothermal water on the wellhead –134 °C and (2) the highest anomalous concentrations of arsenic – 36.7 mg·L-1, compared to other carbonate collectors in the Western Carpathians. The aim of this paper is to explain the observed high concentrations of trace elements, particularly arsenic, to clarify potential sources of arsenic in the geothermal water, to understand the transition mechanism of arsenic in aqueous solution and to determine arsenic speciation in a two-phase system using geochemical modelling. The presented conceptual model and the results from geochemical modelling will contribute to a rational and optimal technological design in future exploitation of geothermal water. Although other factors, such as the confined geothermal structure and the high TDS value are worthy of consideration, the high arsenic water content alone poses the great risk of environmental contamination. To limit this contingency, the re-injection system is considered the optimal method of utilization of this water. Based on results of this study, the general and specific patterns of anomalous arsenic concentrations in geothermal waters have been summarized; not only in the Ďurkov structure, but also in the Western Carpathians region.