In a continuous process for fractionating a C.sub.4 fraction (C.sub.4) by extractive distillation using a selective solvent (LM) in an extractive distillation column (EDK), it is proposed that a dividing wall (TW) is installed in the longitudinal direction in the extractive distillation column (EDK) to form a first region (A), a second region (B) and a lower combined column region (C) and a top stream (C.sub.4H.sub.10) comprising the butanes is taken off from the first region (A), a top stream (C.sub.4H.sub.8) comprising the butenes is taken off from the second region (B) and a stream (C.sub.4H.sub.6) comprising the hydrocarbons from the C.sub.4 fraction which are more soluble in the selective solvent (LM) than are the butanes and the butenes is taken off from the lower combined column region (C).