The relative adsorption in a binary mixture is analyzed by means of molecular dynamics simulations in the canonical ensemble. The Morse function with a repulsive term added was considered as the interaction law among particles. The current analysis was carried out by considering two species whose particles interact with different repulsion degree. Liquid–vapor simulations were developed at low temperatures, and some thermodynamic properties were estimated such as vapor pressure, surface tension and the relative adsorption. As a relevant result for species with the same molecular sizes, an important decrement in vapor pressure and surface tension was observed when softness degree diminishes. The opposite situation occurs for relative adsorption, it was increased when the softness effect diminished. In addition, the vapor pressure and surface tension do not suffer significant dispersion for soft or less-soft particles, when the molecular size of the first species is smaller with respect to the size of the second species.