Measurements of the dynamic response to deformations in aqueous surface with adsorbed DPPC or DPPC/CTAB molecules were done. Based on Maxwellian concept of a visco-clastic surface, the relaxation times of the dynamic surface tension are calculated and compared, indicating the significant influence of low-molecular surfactant on phospholipid activity. Biomedical relevance of the result (in respect to the lung surfactant system) was discussed.