•Effect of vapor-liquid equilibria (VLE) during Fischer-Tropsch Synthesis on the product selectivity and reactor performance.•1-D reactor model taking into account the VLE and the local variation of the chain growth probability.•Simplified VLE model offers an attractive alternative to the complete model.•The VLE has significant influence on the hydrodynamics (liquid holdup and pressure drop).•The catalyst efficiency is strongly affected by the liquid composition. This work analyzes the effect of the vapor-liquid equilibria (VLE) on the productivity and the reactor performance during the Fischer-Tropsch Synthesis (FTS). A reactor model is developed considering the VLE and the local variation of the chain growth probability with temperature and the H2/CO ratio. The model describes the VLE with four different levels of complexity to assess the error introduced by making certain model simplifications. The results show that a simplified VLE model that only accounts for the VLE of CO and H2 offers an attractive alternative since it presents a good accuracy while saving computational time and efforts. Additionally, this work shows that the VLE significantly influences the liquid holdup and the pressure drop. Likewise, the catalyst efficiency is strongly affected by the liquid concentration, and therefore by the VLE. Thus, a full VLE description of reactants and products is needed for the accurate modeling of the FTS reactor.