Abstract: The invention relates to a method for condensing flue gas in combustion plants, and an arrangement of apparatus herefor. In accordance with the invention the flue gas is cooled and humidified by bringing the gas into direct contact with water, whereafter the water vapor in the gas is cooled and condensed, the heat of condensation being recovered by indirect heat exchange. The heat of condensation is transferred partially to a heat absorbing medium, preferably return water in a district heating network, and partially to a circuit in which water is circulated within the plant, this water being used for heating and humidifying the combustion air.