The present invention relates to an exhaust gas guide of a gas turbine, which is situated between the gas turbine and a downstream waste heat boiler or a downstream gas diverter and which comprises a flow channel which has a cross-section expanding in at least some areas in the main flow direction, having installed surfaces influencing the flow. In order to achieve a more compact implementation of the exhaust gas guide and simultaneously avoid or reduce pressure losses, the installed surfaces are implemented as a swirl device generating a leading edge swirl, which is situated in the diverging area of the flow channel and is implemented to distribute the exhaust gas flow uniformly over the flow cross-sectional area upon entry into the waste heat boiler or the gas diverter. Furthermore, the present invention relates to a method for mixing the exhaust gas of a gas turbine with hot exhaust gas streams generated in an auxiliary firing of at least one burner. This thorough mixing is achieved by generating at least one leading edge swirl system in the flow channel.