A rational decision should result in the most optimal level of benefit for an individual. While most conventional economic theories are created under the rationality assumption, past research has shed light on irrational behavior regarding income preference in the presence of social comparison. Solnick and Hemenway found that individuals were willing to give up to 50% of their income in *absolute terms* in exchange for higher *relative* income than significant others. This study (*N *= 314*)* examined which personal characteristics predict such irrational behavior. Specifically, self-monitoring and self-enhancement were hypothesized to be significant and positive predictors for relative income preferences because such individuals are more concerned with their expressive self-presentation and tend to ensure desired public appearances. Moreover, I examined which social group is the most important for income comparison. The results support the hypothesis regarding self-monitoring and self-enhancement as predictors of relative income preference and indicate co-workers to be the most important comparison group.