The analysis of carbon isotope composition in atmospheric CO2 enables determining variations in anthropogenic activities on the global and local level. In this paper, measurements of δ 13C and ∆14C of atmospheric CO2 are carried out in Rijeka, Gornje Jelenje and Parg in order to determine the local Suess effect. δ 13C values of collected samples are measured on a stable isotope mass spectrometer (IRMS - u), and two different techniques are used to determine ∆14C: radiometric (LSC ) and mass spectrometry (AMS). The results show seasonal variations that coincide with changes in the use of fossil fuels for heating and vegetative cycles. The ∆14C of Gornje Jelenje and Parg are relatively similar, but the ∆14C values of Rijeka are lower than Parg by 22 h indicating an increased effect of CO2 emissions of fossil origin. Between Rijeka and clean locations, there are no significant differences in δ 13C values, which is why the local Suess effect cannot be evaluated solely by δ 13C analysis.