Small-angle neutron scattering data were collected from aqueous dispersions of unilamellar vesicles (ULVs) consisting of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine and a homologous series of N,N-dimethyl-N-alkylamine-N-oxides (CnNO, n = 12, 14, 16, and 18, where n is the number of carbon atoms in the alkyl chain). A modeling approach was applied to the neutron scattering curves to obtain the bilayer structural parameters. Particularly, the external 2H2O/H2O contrast variation technique was carried out on pure dioleoylphosphatidylcholine (DOPC) ULVs to determine the hydrophilic region thickness $$ D_{\text{h}} $$ D h = 9.8 ± 0.6 Å. Consequently, the hydrocarbon region thickness $$ 2D_{\text{C}} $$ 2 D C , the lateral bilayer area per one lipid molecule $$ A $$ A , and the number of water molecules located in the hydrophilic region per one lipid molecule $$ N_{\text{W}} $$ N W were obtained from single-contrast neutron scattering curves using the previously determined $$ D_{\text{h}} $$ D h . The structural parameters were extracted as functions of $$ r_{{{\text{C}}n{\text{NO}}}} $$ r C n NO (the CnNO:DOPC molar ratio) and n. The dependences $$ A(r_{{{\text{C}}n{\text{NO}}}} ) $$ A ( r C n NO ) provided the partial lateral areas of CnNOs ( $$ \bar{A}_{{{\text{C}}n{\text{NO}}}} $$ A ¯ C n NO ) and DOPC ( $$ \bar{A}_{\text{DOPC}} $$ A ¯ DOPC ) in bilayers. It was observed that the $$ \bar{A}_{{{\text{C}}n{\text{NO}}}} $$ A ¯ C n NO ’s were constant in the investigated interval of $$ r_{{{\text{C}}n{\text{NO}}}} $$ r C n NO and for n = 12, 14, and 16 equal to 36.6 ± 0.4 Å2, while $$ \bar{A}_{{{\text{C}}18{\text{NO}}}} $$ A ¯ C 18 NO increased to 39.4 ± 0.4 Å2. The bilayer hydrocarbon region thickness $$ 2D_{\text{C}} $$ 2 D C decreased with intercalation of each CnNO. This effect increased with $$ r_{{{\text{C}}n{\text{NO}}}} $$ r C n NO and decreased with increasing CnNO alkyl chain length. The intercalation of C18NO changed the $$ 2D_{\text{C}} $$ 2 D C only slightly. To quantify the effect of CnNO intercalation into DOPC bilayers we fit the $$ 2D_{\text{C}} (r_{{{\text{C}}n{\text{NO}}}} ) $$ 2 D C ( r C n NO ) dependences with weighted linear approximations and acquired their slopes $$ \Delta d $$ Δ d .