Due to the excessive emission of carbon dioxide (CO2) caused by industrial activities in various sectors, carbon dioxide gas absorption techniques have been considered in order to reduce greenhouse gas emissions. In this research, the effect of ion exchange polystyrene resin modification by triethylenetetramine (TETA) on the performance of carbon dioxide adsorption by the resin was studied. In this way, the surface of polystyrene resin was impregnated with TETA amine (physical modification) and also in another process, TETA amine was attached to polystyrene resin with the help of a chemical reaction (chemical modification). Physical and chemical modification by TETA amine was done both on polystyrene beads and on powdered polystyrene resin. BET specific surface area for bead and powdered resin was measured as 0.4443 m2/g and 2.9205 m2/g, respectively. The modified resins were identified by infrared spectrometer (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and the performance of the modified resins in carbon dioxide adsorption was also investigated. The presence of amine groups as a modifying agent in the FTIR spectra of the physical and chemical modified polystyrene resins was confirmed and was an indication for the successful preparation of the modified resin. The increase in the mass percentage of nitrogen on the surface of the chemically modified resin compared to the original resin (powder and bead) which was measured by SEM-EDS analysis, indicates the presence of TETA amine on the surface of the polystyrene resin after the chemical reaction. According to the results of TGA analysis, the thermal stability of the modified resin increased compared to the initial resin. Finally, the performance of the modified resins in adsorbing CO2 gas was investigated by adsorption. Investigations showed that powder resins that are physically impregnated by TETA show the highest adsorption of CO2 and the lowest adsorption rate is related to prist