Groundwaters of the Wygnanowice area (Poland) were studied for dissolved inorg. C and C-13/C-12 isotope ratio in CO2. The concns. of CO2 in spring draining porous Quaternary rocks were higher than that in soil waters and water in solid rocks of Cretaceous aquifer, which are drained to the spring and the Gielczew river. The anal. of C-13 isotope showed a high CO2 concn. in the spring water because of biogenic processes in peats and/or fossil soils. The enrichment of water in CO2 took place during infiltration below the level of soil.