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The Planchón – Peteroa Volcanic Complex exhibits two active degassing areas: Peteroa crater, PC, and peripheral hydrothermal areas, analyzed in three sampling sites, namely Valle Baños del Azufre, VBA, Valle del Peñón, VP and Valle Valenzuela, VZ. This prospective study was designed to investigate the soil diffuse emissions of CO 2 at this volcanic complex. The survey consisted of 560 measurements of CO 2 soil diffuse flux and temperature carried out at PC, VBA, VP. The results of this work show that diffuse CO 2 is emitted at PC through two well-defined diffuse degassing structures and flux distribution that can be modeled by combining two log-normal populations. Here, the main source of soil CO 2 is a shallow aquifer recharged by steam condensation and meteoric fluids that interact with rising magmatic gases. The carbon isotopic signature reveals that CO 2 diffuse degassing is affected by secondary soil processes during its ascent. The total diffuse CO 2 output at the surveyed area of PC, which covers ̴77,000 m2 around the crater fumarolic field, is 6.49 ± 0.32 t d−1. Soil diffuse emissions at the hydrothermal peripheral sites, VBA and VP, were studied covering a total area of ̴590,000 m2. These emissions are characterized by poorly defined diffuse degassing structures and flux distributions that can be modeled by combining three log-normal populations, which suggest that multiple sources feed CO 2 diffuse emissions. In concordance, the isotopic analysis also suggests a mixed source of CO 2 and degassing affected by secondary processes that modify the original isotope composition. CO 2 soil degassing at VZ shows a clear relation with the vegetated areas of the soil. The minimum endogenous CO 2 output estimation here proposed for the Planchón – Peteroa Volcanic Complex is that of PC, ̴6.5 t d−1. The thermal energy release was computed for PC, and the estimation is 2.57 ± 0.53 MW. • Planchón – Peteroa Volcanic Complex emits over 6 tons per day of volcanic- hydrothermal diffuse carbon dioxide. • Deep CO 2 is emitted through the active crater of Peteroa volcano. The peripheral hydrothermal sites emit mainly biogenic CO 2. • The carbon isotopic composition suggests that secondary processes deeply modify the original isotope composition. • The thermal energy release was estimated by assessing the flux of steam. The heat flux at Peteroa crater is 2.5 MW. [ABSTRACT FROM AUTHOR]