An adiponitrile/methylglutaronitrile preparation process includes distilling a reaction stream to obtain stream 3 depleted in pentenenitriles (bottom product) and stream 4 enriched in pentenenitriles (top product); extracting stream 3 obtaining stream 6 enriched with extractant (top product) and stream 7 depleted in extractant (bottom product); distilling stream 6 obtaining stream 8 comprising the catalyst (bottom product) and stream 9 comprising the extractant (top product); distilling stream 7 obtaining stream 10 (bottom product) and stream 11 comprising the extractant (top product); distilling stream 10 obtaining stream 12 comprising catalyst degradation products, at least one promotor, adiponitrile and methylglutaronitrile (bottom product) and stream 13 comprising pentenenitriles (top product); distilling stream 12 obtaining stream 14 comprising catalyst degradation products and the promotor(s) (bottom product) and stream 15 comprising adiponitrile and methylglutaronitrile (top product); distilling stream 15 obtaining stream 16 comprising adiponitrile (bottom product) and stream 17 comprising methylglutaronitrile (top product).