The dynamic surface properties of mixed solutions of a cationic surfactant - cetyltrimethylammonium bromide (CTAB) - and different types of deoxyribonucleic acid in both linear (ctDNA) and plasmid (pDNA) forms were studied by surface tensiometry and dilational surface rheology. The dynamic surface elasticity and the dynamic surface tension depended strongly on the DNA type. The adsorption layers of ctDNA/CTAB solutions exhibited strong elastic behavior in a wide range of surfactant concentrations. Contrariwise, the addition of plasmid DNA altered the dynamic surface elasticity of CTAB solutions only slightly. The significant difference in the size of macromolecules, their conformation, and, thereby, their effective charge leads to the formation of DNA/CTAB complexes of different surface activity and causes drastic changes in the rheology of the adsorption layer. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.