Abstract:There have been studies on comparability of test results in Computer-Based Testing (Henceforth CBT) and PaperBased Testing (Henceforth PBT) considering key factors associated with test results in different countries with different languages and technological backgrounds. The main purpose of the current study was to discover the equivalency of test scores on PBT and CBT in the English achievement test in Payame Noor University (PNU) among undergraduate students. It also intended to investigate if there was any relationship between computer attitude and testing performance on CBT. Based upon the quantitative and qualitative data, some major findings were revealed. Firstly, there was statistically significant difference between two sets of mean scores. Furthermore, based on descriptive results, in comparing the results of computerized and paper-based tests, students showed better performance on PBT than CBT. The results of this study support the necessity of doing comparability studies in higher educational contexts before substituting CBT for PBT or including it in the system. Then, computer attitude had not any interaction with testing performance on CBT among Iranian undergraduate students in PNU. Finally, the results of interview supported the quantitative findings, i.e. participants mostly showed high preference for computerized test and liked CBT more than PBT but due to some justifications and habit of taking tests traditionally, they performed better on PBT.