The principal technologies for CO2 capture (including absorption, adsorption, membrane separation, cryogenic separation) and for producing rich CO2 process streams by CO2/O-2 combustion cycles are reviewed in summary form and their present limitations are identified. The latter include uncertainties regarding their technical design, short- and long-term operational problems, and economic feasibility. In particular, the current lack of knowledge of physical, chemical and rate data, contact mechanisms, solvent, adsorbent and membrane stability, corrosion, fouling, and by-product generation are considered. These problems together with the need to improve capture rates, raise capture efficiencies and lower capture costs are then used for suggesting directions of future research and development