Since Peng and Robinson proposed their cubic equation of state (cubic EoS) in 1976, several attempts were made to improve its performance and to extend its application to an increasing number of substances. Many authors have focused in vapor pressure calculation, which in great part signifies the proposal of a new alpha function for the attractive term. In this work, 20 alpha function models were compared in vapor pressure estimation for 56 compounds with the Peng-Robinson EoS. The values calculated with the EoS were compared with values obtained from the DIPPR database. The parameters are presented as an useful data bank for future applications. With these results, it was possible to show which model had the best performance for each class of compounds, which is important information for the development of new alpha function models. The alpha functions of Androulakis et al., Schwartzentruber et al., and Almeida-Aznar-Telles obtained the best results among all the models evaluated.