The purpose of this study is to examine negative IT performances produced by irrational fashion-mimic IT investments in firms. Since most studies have been carried out on the assumption of rational investment decisions, many of them have revealed positive investment process and performances in firms. However, fashion-mimic investments to follow the paths of market leaders rather than rational investment decisions have been of frequent occurrence in many firms. This study divided types of mimic investments into subgroups where one subgroup has fashion-mimic properties and the other subgroup retains rational-mimic properties. We compared differences in performance of these subgroups to investigate effects of irrational investments in IT projects. The results indicated that there are differences in performance between fashion-mimic and rational-mimic investments. Additional analysis also revealed differences in performance at the presence of CEO control in the case of fashion-mimic investment subgroup.