It has been shown that the interactions of nanoparticles with lipid and lipid–peptide monolayers mimicking the lung surfactant strongly depend on the physical properties of the nanoparticles, their size, and on the physical properties of the surface film. Hydrophobic nanoparticles have been found inserting into fluid phases of lipid monolayers. They have an adverse effect on the functional properties of the pulmonary surfactant, which strongly depends on the nanoparticle size. But how NPs disturb or inhibit this surfactant function still remains unclear. Experimental evidences gathered under physiologically relevant conditions or from in vivo studies are still lacking. The present review summarizes systematic investigations on simplified model systems of the lung surfactant using highresolution bioanalytical techniques that have provided valuable hints and indications about the interactions of NPs with the surfactant layer at the molecular level. Further studies are needed in particular for a more detailed understanding of the mechanism by which NPs are capable of crossing the surfactant barrier even though they experience a very different and individual free energy barrier at the interface.