Two laboratory studies examined the potential differences in the susceptibility to faking between a construct-oriented Situational Judgment Test (SJT) that measured conscientiousness and a traditional self-report measure of personality (NEO-FFI). In both studies, the mean differences between the honest and faked conscientiousness scores indicated that the NEO-FFI was more susceptible to faking than the SJT. In Study 1, we applied a within-subjects design (N = 137) and analyzed these differences in light of selected predictor variables derived from models of faking behavior. As a result, faking on the SJT was explained by cognitive ability alone, whereas faking on the NEO-FFI was also dependent on other personality traits that are associated with the ability to fake. In Study 2 (N = 602), the susceptibility to faking was predicted by differences in faking styles. The results of the mixed Rasch model analyses indicated profound differences in the measures in terms of the way the response scale was used.