A method for preparing substantially enantiopure 3-hydroxy carboxylic acids or esters of the general formula (III) by reacting racemic oxetan-2-ones of the general formula (I) with compounds R3-OH of the general formula (II) in the presence of a lipase from Candida antartica or Burkholderia plantarii, and separating the resulting products of the formula (III) and (IV) from one another