ABSTRACT: This article analyzes the chemical composition and mine water quality in the Gbely lignite deposits, thus clarifying mine water chemical composition processes. The results document boreholes in this deposit, and especially groundwater from the overlying and underlying collectors, and groundwater pumped from boreholes lined in both collectors, in the deep sublayer and behind the fault zones. The chemical composition and quality of groundwater were evaluated in 93 wells. Of these, 29 were in overlying collector, 32 were in the underlying collector and 30 were in the overlying and underlying collectors, in the deep sublayers and behind fault zones. The chemical analysis was derived from archival sources, from Mine Čáry, Inc (2010) and ŠGÚDŠ (2010). The following groundwater contents were observed; (1) the overlying collectors contained a prevalence of calcium, magnesium and hydrogencarbonate ions, and the highest manganese and phosphate content, (2) underlying collectors are dominated by calcium, magnesium and hydrogencarbonate, with higher sodium concentration and the highest concentration of H2SiO3 and (3) the boreholes lined in both collectors and those in the deep sublayer and behind the fault zones were most varied in chemical composition. The assessment of the mine water’s chemical composition and quality required by Government Decrees 496/2010 and 269/2010 forms a very important part of this article. Sources of pollution resulting from coal mining in the Gbely lignite deposits and the Čáry mine, and the mine water discharged into surface streams are all discussed herein.