The absorption of CO₂ in aqueous NH₃ solutions occurs with high efficiency and loading capacity at room temperature and atmospheric pressure producing the ammonium salts of bicarbonate (HCO₃⁻), carbonate (CO₃²⁻), and carbamate (NH₂CO₂⁻) anions. ¹³C NMR spectroscopy at room temperature has been proven to be a simple and reliable method to investigate the speciation in solution of these three ionic species. Fast equilibration of HCO₃⁻/CO₃²⁻ anions results in a single NMR peak whose chemical shift depends on the relative concentration of the two species. A method has been developed to correlate the chemical shift of this carbon resonance to the ratio of the two anionic species. Integration of the carbamate carbon peak provided the relative amount of this species with respect to HCO₃⁻/CO₃²⁻ pair. No other species was detected in solution by ¹³C NMR, and no solid compounds separated out under our experimental conditions. Finally, the relative amount of HCO₃⁻, CO₃²⁻, and NH₂CO₂⁻ in solution have been correlated to the molar ratio between free ammonia in solution and absorbed CO₂.