The topic of our research is the detection of concealed information based on ERP (Event Related Potential). As a method to detect concealed information there is CIT (Concealed Information Test). CIT is used to detect intentionally concealed information, for example crime-related information, with subject's physiological response to presented stimuli. We used visually CIT based on P300 in the experiment. There are three kinds of stimuli in CIT. One is 'Probe', which is related to concealed information. The other is 'Irrelevant', which is not related with it but consists of same category as Probe (ex; place, time and so on). And the other is 'Target', which is for calling subject's attention to the experiment. In CIT, the subject's reaction to those presented stimuli are measured and compared with each other categories. If the reaction to Probe are different with one to Irrelevant the subject is considered as he knows Probe. Although Words are often used as stimulus in this kind of study, we assume that pictures are better as the stimulus in CIT. In this study, we investigated the difference between the word stimuli and picture stimuli in CIT. We use Japanese words or pictures as the stimulus and compare the amplitude of P300 as reaction to those stimuli. It is showed that picture stimuli are better than word stimuli for CIT.