The invention relates to a method for producing optionally alkyl-substituted 1,4-butanediol by means of two-stage catalytic hydration in the gas phase, comprising the following steps: a) a gas stream of C4-dicarboxylic acid or a derivative thereof is fed into a first reactor and the gas phase is catalytically hydrated so as to obtain a product mainly containing optionally alkyl-substituted y-butyrolactone; b) the obtained product stream is fed into a second reactor and the gas phase is catalytically hydrated so as to obtain optionally alkyl-substituted 1,4-butanediol; c) the desired product is separated from intermediate products, by-products, and an optionally unreacted starting material. A catalyst comprising = 95 percent by weight of CuO and = 5 percent by weight of an oxidic carrier is used in each hydration stage. The product mixture obtained in the first hydration step is introduced into the second hydration stage without further cleaning said product mixture.