NOVELTY - The method for separating a C4 fraction by means of extractive distillation using a selective solvent (1) by way of counter-flow of the C4 fraction and of the selective solvent in a liquid phase in a distillation unit, comprises separating a head flow (3) comprising butanes and butenes from the C4 fraction and a bottom flow (6) comprising the selective solvent and the remaining components of the C4 fraction with the exception of the butanes and butenes, and outgassing the selective solvent from the fraction in an additional step.    USE - Method useful for separating a C4 fraction by means of extractive distillation.    ADVANTAGE - The method ensures economical separation of C4 fraction.    DETAILED DESCRIPTION - The method for separating a C4 fraction by means of extractive distillation using a selective solvent (1) by way of counter-flow of the C4 fraction and of the selective solvent in a liquid phase in a distillation unit, comprises separating a head flow (3) comprising butanes and butenes from the C4 fraction and a bottom flow (6) comprising the selective solvent and the remaining components of the C4 fraction with the exception of the butanes and butenes, outgassing the selective solvent from the fraction in an additional step, and extracting energy from the distillation unit between the extraction point for the head flow and the extraction point for C4 fraction in the distillation unit. The point from which energy is deducted is positioned in the distillation unit, where 30-70 wt.% of the total number of theoretical separation stages present above extraction point for the C4 fraction is arranged between the same point and extraction point for the C4 fraction. The energy quantity is deducted that corresponds to a temperature reduction of up to 15 degrees C. The distillation unit comprises a first column and a second column, which are connected among one another with a liquid direction and a flow direction (7). The liquid from the first column is guided over the liquid line in the second column and the flow from the second column is guided over the flow direction into the first column, where the extraction point is arranged for the C4 fraction in the upper area of the second column. A theoretical separation stage is carried out above the extraction point for the C4 fraction, where the energy is deducted from the liquid direction and/or the flow direction. The liquid and/or gas deducted at the points from the distillation unit is cooled in an external cooler and is recirculated into the distillation unit at the same points or at a point different from the point of the deduction of the liquid and/or the gas. The liquid and/or the flow is guided over an interior cooler in the distillation unit. N-methylpyrrolidone with 8.3 wt.% of water, dimethylformamide, acetonitrile or a mixture with water and/or alcohol is used as the selective solvent.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of a distillation unit with two columns.    Selective solvent (1)    Head flow (3)    Interconnector (4)    Bottom flow (6)    Flow direction. (7)