Abstract: This invention relates to a method for the separation of low molecular-weight aromatic compounds, e.g. vanillin and dehydrodivanillin, from lignin, alkali, and from each other, in alkaline aqueous solutions. According to the method, the separation is effected by means of a cationic ion-exchange resin in its sodium salt form, e.g. of a strong sulphonic acid type or weak carbonic acid type, from which the substances adsorbed are removed by elution. The resin may be crosslinked to the extent of 2-16% divinylbenzene. The substances adsorbed onto the ion-exchange resin are appropriately eluted by either water alone, or by application of an aqueous sodium-salt solution (e.g. Na.sub.2 CO.sub.3) followed by water.