A process is described for obtaining high-purity 1-butene starting from C4 hydrocarbon mixtures containing isobutene, n-butane, isobutane, 1,3-butadiene, 1-butene, 2-butenes and also optionally C3 and C5 hydrocarbons, comprising the following stages: conversion of isobutene effected in a double stage, wherein each stage consists of one or more reactors followed by a distillation column for the recovery of the reaction product; recovery of the excess alcohol; recovery of 1-butene using at least two distillation columns; characterised in that it also uses a further conversion stage, consisting of one or more reactors in series, for completing the isobutene removal.