Carbon nanotubes (CNTs), granular activated carbon (GAC), and zeolites were modified by 3-aminopropyltriethoxysilane (APTS) and were selected as adsorbents to study their physicochemical properties and adsorption behaviors Of CO2 from gas streams. The surface nature of these adsorbents was changed after the modification, which make them adsorb more CO2 gases. Under the same conditions, the modified CNTs possess the greatest adsorption capacity of CO2 followed by the modified zeolites and then the modified GAC. The mechanism of CO, adsorption on these adsorbents appears mainly attributable to physical force, which makes, regeneration of spent adsorbents at a relatively low temperature become feasible. The APTS-modified CNTs show good performance Of CO2 adsorption as compared to many types of modified carbon and silica adsorbents reported in the literature. This suooests that the APTS-modified CNTs are efficient CO2 adsorbents and that they possess potential applications for CO2 capture from gas streams.