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 ##STR00001## where the radicals have the following meaning: R.sup.1, R.sup.2, R.sup.3 independently of one another H; C.sub.1-C.sub.10-substituted or unsubstituted alkyl, substituted or unsubstituted aryl or hetaryl, where R.sup.1 and R.sup.2 may not simultaneously have the same meaning.