The volume method is used to evaluate the productive potential of unexploited and minimally exploited geothermal fields. The distribution of Pan in shallow groundwaters delimits the geothermal fields. This approach is substantiated by the good correspondence between zones of high CO(2) flux, and the areal extension of explored geothermal systems of high enthalpy (Monte Amiata and Latera), medium enthalpy (Torre Alfina) and low enthalpy (Viterbo). Based on the data available for geothermal fields either under exploitation or investigated by long-term production tests, a specific productivity of 40 th(-1) km(-3) is assumed. The total potential productivity for the recent volcanic areas of Latium is about 28 x 10(3) th(-1), with 75% from low-enthalpy geothermal fields. 17% from medium-enthalpy systems, and 8% from high-enthalpy reservoirs. The total extractable thermal power is estimated to be 2220-2920 MW, 49-53% from low-enthalpy geothermal fields, 28-32% from medium-enthalpy systems, and 19-20% from highenthalpy reservoirs. (C) 2010 Elsevier Ltd. All rights reserved.