Because electricity production is one of the major sources of pollution, and at the same time is the most centralised one, environmental issues in power system operation and planning are gaining ever-increasing attention. It is very difficult to compare environmental impacts of various electricity generation technologies and fuel types because they are extremely divergent. The most widely accepted common denominator today is the so-called external cost by which a monetary value is associated with environmental damage. In this paper, damages to human health resulting from Croatian thermal power plants annual operation are presented. Stack emissions have been translated into ambient concentrations by atmospheric dispersion modelling. Existing data on relations between human health degradation and ground concentrations of the analysed pollutants have been used. Geographic information software has been used in order to account for spatially dependent data. Monetary values have been assigned to the estimated human health damage. External costs resulting from impact of Croatian thermal power plants airborne emissions on human health have been calculated. The total Croatian thermal power system external costs, resulting from impacts on human health, are presented and discussed. (c) 2004 Elsevier Ltd. All rights reserved.