The adsorption properties of diastereomerically pure cis- and trans-2-n-alkyl-5-methoxy-1,3-dioxanes (alkyl: n-C3H7, n-C4H9, and n-C5H11) at the air/water inter-face at 295 K were investigated using surface tension measurements of surface-chemically pure solutions. The surface parameters, i.e., the standard free energy of adsorption, Delta G(ad)(o), the minimum surface area demand per molecule adsorbed, A(min), and the surface interaction parameter, HS, reveal distinct differences with respect to the molecules' stereochemistry. The adsorption parameters of these compounds are compared with those of the related cis- and trams-2-n-alkyl-5-hydroxy-1,3-dioxane derivatives. The surface parameters standard free energy and surface interaction of the corresponding homologous series of the cis- and trans-2-n-alkyl-5-methoxy-1,3-dioxanes and of the cis- and trans-2-n-alkyl-5-hydroxy-1,3-dioxanes differ considerably. However, the cross-sectional areas of the two cis and trans homologous series each approach practically identical limiting values.