A process for preparing 3-pentenenitrile by hydrocyanating 1,3-butadiene, which comprises the following process steps: (b') distillation of 1,3-butadiene comprising water, 1- and 2-butenes and a stabilizer in a distillation apparatus K4 to obtain a stream 15 as the bottom product, which comprises dried 1,3-butadiene, 1- and 2-butenes and the stabilizer, and a stream 16 as the top product, which comprises an azeotropic 1,3-butadiene/water mixture, condensation of the stream 16 in a condenser W, transfer of the resulting condensate (stream 17) into a phase separation apparatus, recycling of the upper liquid phase (stream 18) consisting of 1,3-butadiene as reflux to the column K4, and discharge of the lower liquid aqueous phase (stream 19), (a) reaction of stream 15 in a reactor R1 with hydrogen cyanide over at least one catalyst (stream 6d) to obtain a stream 1 which comprises 3-pentenenitrile, 2-methyl-3-butenenitrile, the at least one catalyst in the form of homogeneously dissolved nickel complexes and phosphorus ligands, unconverted 1,3-butadiene, and 1- and 2-butenes, with or without residues of unconverted hydrogen cyanide, (b) distillation of stream 1 in a distillation apparatus K1 to obtain a stream 2 as the top product, which comprises the predominant portion of the 1,3-butadiene from stream 1, and to obtain a stream 3 as the bottom product, which comprises 3-pentenenitrile, the at least one catalyst, 2-methyl-3-butenenitrile, 1- and 2-butenes and the remaining proportion of the 1,3-butadiene from stream 1 which has not been removed in stream 2, (c) distillation of stream 3 in a distillation apparatus K2 to obtain a stream 5 at a side draw of the column, which 3-pentenenitrile and 2-methyl-3-butenenitrile, a stream 6 as the bottom product, which comprises the at least one catalyst, and a stream 4 as the top product, (d) compression of stream 4 in the compressor VI, discharge of a gaseous substream 4b which comprises 1- and 2-butenes, transfer of the compressed stream 4a into the condenser W1, combined cond. With stream 2 from b) in combined condensation of this stream 2 from b) and transfer of the condensate as stream 9, partly as reflux to the column K1 (stream 9b), partly as return stream into the reactor R1 (stream 9a), and (e) distillative separation of stream 5 to obtain 3-pentenenitrile and 2-methyl-3-butenenitrile. (b') distillation of 1,3-butadiene comprising water, 1- and 2-butenes and a stabilizer in a distillation apparatus K4 to obtain a stream 15 as the bottom product, which comprises dried 1,3-butadiene, 1- and 2-butenes and the stabilizer, and a stream 16 as the top product, which comprises an azeotropic 1,3-butadiene/water mixture, condensation of the stream 16 in a condenser W, transfer of the resulting condensate (stream 17) into a phase separation apparatus, recycling of the upper liquid phase (stream 18) consisting of 1,3-butadiene as reflux to the column K4, and discharge of the lower liquid aqueous phase (stream 19), (a) reaction of stream 15 in a reactor R1 with hydrogen cyanide over at least one catalyst (stream 6d) to obtain a stream 1 which comprises 3-pentenenitrile, 2-methyl-3-butenenitrile, the at least one catalyst in the form of homogeneously dissolved nickel complexes and phosphorus ligands, unconverted 1,3-butadiene, and 1- and 2-butenes, with or without residues of unconverted hydrogen cyanide, (b) distillation of stream 1 in a distillation apparatus K1 to obtain a stream 2 as the top product, which comprises the predominant portion of the 1,3-butadiene from stream 1, and to obtain a stream 3 as the bottom product, which comprises 3-pentenenitrile, the at least one catalyst, 2-methyl-3-butenenitrile, 1- and 2-butenes and the remaining proportion of the 1,3-butadiene from stream 1 which has not been removed in stream 2, (c) distillation of stream 3 in a distillation apparatus K2 to obtain a stream 5 at a side draw of the column, which 3-pentenenitrile and 2-methyl-3-butenenitrile, a stream 6 as the bottom product, which comprises the at least one catalyst, and a stream 4 as the top product, (d) compression of stream 4 in the compressor VI, discharge of a gaseous substream 4b which comprises 1- and 2-butenes, transfer of the compressed stream 4a into the condenser W1, combined cond. With stream 2 from b) in combined condensation of this stream 2 from b) and transfer of the condensate as stream 9, partly as reflux to the column K1 (stream 9b), partly as return stream into the reactor R1 (stream 9a), and (e) distillative separation of stream 5 to obtain 3-pentenenitrile and 2-methyl-3-butenenitrile.