Here, we aim to understand whether the ability of the water model to reproduce experimental surface tension, the inclusion of long-range van der Waals interactions, or both are critical for the correct description of lipid monolayers in MD simulations. Our results pave the way toward more realistic simulations of lipid monolayers with applications in wide range of fields from surfactant science to membrane biophysics and pharmacology. The methodological advancement following our results is not limited only to monolayer simulations. Indeed, monolayer surface tensions are used as target parameters in the recently introduced automatic parameterization strategy for C36/LJ-PME, which is expected to have wide range of applications to in biomolecular simulations of systems with complex compositions.