A method and a plant for producing liquid CO 2 out of combustion flue gases wherein the flue gas is partially condensed in a single stage phase separation, the single stage phase separation comprising at least one heat exchanger (11,17) and a separation drum (19), wherein the at least one heat exchanger (11,17) is cooled by expanded offgas (23) and expanded liquid CO 2 (3.3) and wherein a first paid of the expanded CO 2 (3.3) is separated after having passed the at least one heat exchanger (17) into liquid CO 2 and gaseous CO 2 in an additional separation drum (33), wherein the gaseous CO 2 (3.4) and the liquid CO 2 (3.5) of the additional separation drum (33) are expanded to a first pressure level (flag 7d') wherein a second part of the liquid CO 2 (3.6) of the separation drum (33) is expanded to a second pressure level (flag 7e') for cooling the flue gas in the at least one heat exchanger (17).