The paper deals with soil quality assessment and evaluation of soil functions. Because of numerous potential land uses, it is not possible to evaluate soil quality by an only index for all recent and future land uses. Soil quality assessment thus has to be related to particular recent or planned future land use. Nevertheless, partial soil functions can be evaluated alone and then score values of the most important functions can be combined into soil quality index. In this study we attempt to describe and quantify the capability of soil to function as a filter in the cycle of specific organic pollutants. The basis of the approach is comprehension and numerical expression of key physical and chemical processes which account for soil filtration function. Relevant processes were described using soil and environmental indicators. Minimum data set of indicators used for evaluation included quantity and quality of soil organic matter, humus layer thickness, clay content and soil thickness as soil quality indicators and precipitation as an environmental factor. As a demonstration of practical application, data from existing database of selected soil profiles of Complex Soil Survey in the Slovak Republic were used for calculation of a filtration capability score. Indicators were transformed and normalized by soil scoring functions, combined into equation for score of filtration capability and five categories of filtration capability were set up. The map of categories of the soil filtration capability in the Slovak Republic was processed using methods of spatial statistics.