The invention relates to a method for producing cyclic lactams of formula (II) by reacting a compound (I) of formula (I) with water in the presence of an organic, liquid dilution agent in the liquid phase. In formula (II), n and m respectively can have the values 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 and the sum of n+m is at least 3, preferably at least 4 and R1 and R2 represent C1-C6 alkyl, C5-C7 cycloalkyl or C6-C12 aryl groups. In formula (I), R1, R2, m and n are defined as above and R represents nitrile, carboxylic acid amide and carboxylic acid groups. The inventive method is characterized in that a) compound (I) is reacted with water in the liquid phase in the presence of an organic, liquid dilution agent (III) to form a mixture (IV) containing a lactam (II) and said mixture (IV) is subjected to an aqueous treatment to obtain a two-phase system.