Optionally alkyl-substituted 1,4-butanediol is prepared from C4-dicarboxylic acids and/or of derivatives thereof by: a) a gas stream of the C4-dicarboxylic acid or the derivative thereof in a first reactor in the gas phase to obtain a product which contains mainly optionally alkyl-substituted γ-butyro-lactone; b) removing succinic anhydride from the product of step a); c) catalytically hydrogenating the product of step b) in a second reactor in the gas phase to obtain optionally alkyl-substituted 1,4-butanediol; d) removing the desired product from intermediates, by-products and any unconverted reactants; and e) optionally recycling unconverted intermediates into one or both hydrogenation stages. The catalysts employed in each of the hydrogenation stages comprise ≦95% by weight of CuO, and ≦5% by weight of an oxidic support, and the second reactor has a higher pressure than the first reactor.