Interaction of sodium pyrene-3-sulfonate (NaPyS) with different lipid monolayers has been studied by fluorescence and reflection spectroscopy, surface pressure measurements, and electrochemical methods. NaPyS interacts with dioctadecyldimethylammonium bromide (DOMA) monolayers at the air/water interface due to the Coulombic interaction with the positively charged head groups, while no interaction with dipalmitoylphosphatidylcholine (DPPC) monolayers has been noticed. NaPyS from solution also influenced DOMA monolayers which were transferred from the air/water interface to the mercury surface. The enhancement of the transport of cadmium ions across a DOMA film modified by NaPyS adsorption was observed.