The ratio of CO2 emissions from power plants to natural emissions is a measure of the environmental impact associated with geothermal power production. Emissions from Icelandic geothermal power plants amounted to 1.6 x 10(8) kg year(-1) in 2002. Two independent estimates of natural CO2 emissions range between 1 x 10(8) and 2 x 10(9) kg year(-1). Thus, power plant emissions are significant compared to estimated total emissions (i.e., not less than 8-16%). However, direct CO2 flux measurements from four of the approximately 40 geothermal/volcanic systems in the country amounted to 3 x 108 kg year(-1), indicating that these estimates of the total natural flux may be too low. (c) 2004 CNR. Published by Elsevier Ltd. All rights reserved.