ABSTRACT: This paper presents the results of chemical analys is of surface and groundwater samples obtained from the mining area Kolársky vrch (Malé Karpaty Mts.). Chemical composition of surface and groundwater is influenced by mine water and sludge water from tailing ponds. In surface and groundwater were detected high concentration of sulphates, Fe, Al, As and Sb. Total arsenic concentration in the analyzed waters vary between 2 to 46 400 ug.l-1 with dominance of As(+V) species. Arsenic distribution in groundwater is characterized in partial pe-pH stability diagrams for dissolved arsenic species. Redox potential (Eh) and pH are the most important factors controlling As speciation. Results of speciation calculations by the hydrogeochemical code PHREEQC-2 in the form of SI values for selected minerals (calcite, goethite, gypsum, rhodochrosite, siderite and scorodite) and mineral phases (amorphous Al(OH)3, amorphous Fe(OH)3) are discussed. Positive values of SI for amorphous Fe(OH)3 and goethite was calculated for all groundwater samples, Saturation with respect to As(+V) mineral scorodite is not reached due to relatively low Fe(+III) concentrations. However, water is supersaturated with respect to amorphous Fe(OH)3 and goethite, suggesting that adsorption on these mineral phases controls for dissolved arsenic concentrations.