The present invention relates to a process for producing 4-hydroxybutyraldehyde, characterized in that allyl alcohol dissolved in polar solvents is reacted with CO and H2 in the presence of a catalytic system which is formed from a rhodium complex and a cyclobutane ligand which contains at least two trans-coordinated 3 5-dialkylphenylphosphinomethyl groups, with the exclusion of catalysts which contain an aliphatic, araliphatic or cycloaliphatic phosphine as ligand.