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Nitrogen-doped activated carbons with high surface areas obtained from resorcinol and formaldehyde resins were evaluated as CO 2 adsorbents in a simulated flue gas stream under anhydrous and humid conditions. These carbons were prepared using two approaches, namely ammonia treatment without nitric acid pre-oxidation and amination after preoxidation. The pre-oxidation of activated carbons considerably enhanced the nitrogen incorporation during the amination process. The amination temperature affects the content and type of nitrogen incorporated onto the carbon surface, as determined by X-ray photoelectron spectroscopy, which enhances the specific adsorbent-adsorbate interaction for CO 2 in humid conditions. The presence of H 2 O in the feed gas significantly decreased CO 2 adsorption for a very low nitrogen content of virgin activated carbon. A sample prepared via the amination of pre-oxidized carbon at 700°C (NORF700) exhibited excellent tolerance to moisture and the highest CO 2 capacity of 2.10 mmol/g in a 7% CO 2 /83% N 2 /10% H 2 O wet stream at 50°C and 130 kPa. The high performance of NORF700 was ascribed to its high surface area, adequate micropore volume, and high amounts of pyrindinic-like and pyrrole-like nitrogen species. The results indicate that nitric acid preoxidation followed by ammonia treatment at 700°C is an appropriate process for preparing adsorbents for CO 2 separation in post-combustion applications.