In this study, we investigate the effects of a wide range of carbon dioxide (CO2) concentrations in flue gas on postcombustion capture of CO2 using chemical absorption with monoethanolamine (MEA) and ammonia. The applied range of flue gas CO2 concentrations represents typical profiles of emission sources associated with industrial applications. Modeling of the process chemistry to study the effect on process performance reveals that with an appropriate design of the capture process, the specific heat requirement for solvent regeneration decreases as the CO2 content of the flue gas increases. At the same time, the specific cooling requirement of the process increases and the appropriate shape of the temperature profile in the absorber becomes critical at high flue gas CO2 concentrations, especially when using MEA as absorbent, which has high reactivity and a high heat of reaction compared with ammonia. For both solvents investigated it is difficult to achieve high capture rates at low concentrations of CO2.