Important improvements have been achieved in the study of diVuse CO2 degassing from soil for what concerns both measuring and data treatment methods. Methods and applications to several study cases regarding the defnition of the spatial extent of the anomalous degassing areas and quantifcation of the amount of released CO2 are reviewed. The results show that the CO2 is released by degassing structures generally connected to tectonic and volcanic structures, large amount of gas is released by soil diVuse degassing and that the energy release associated to diffuse degassing is important in the energetic balance of the volcanic-hydrothermal systems. Quantifcation of the CO2 release represents a fundamental constrain for the modelling of the hydrothermal fuids ascent. Hence the quantifcation and monitoring of gas and energy fuxes associated with diVuse degassing may constitute important tools for the comprehension of the system dynamic and therefore for the surveillance of volcanic activity.