Superplasticizers typically work within the first 2 hours of cement hydration. Therefore, early hydration products have to be studied to investigate their mode of action. The experiments in this paper demonstrate that ettringite is a preferred phase for the adsorption of polycondensate or polycarboxylate based superplasticizers, whereas polycondensate amd polycarboxylate practically show no signs of adsorption. For polycarboxylate adsorption, time of addition to ettringite is not important whereas polycondensates adsorb much less when addition is delayed. Adsorption does not seem to occur and therefore cannot explain the different behavior of polycondensates. The presence of superplasticizers during ettringite formation reduces the crystal size of ettringite. The effect is particularly strong for polycondensate superplasticizers. There was no influence on ettringite morphology or quantity formed found.