The present study examined the effect of a set size of stimuli (number of stimuli) on an amount of inhibition observed in the word-word task, picture-word task, and picture-picture task. In these tasks, subjects were required to name or read target (picture or word), ignoring distractor (picture or word). It was hypothesized that when the set size of stimuli is small, some stimuli are primed to response, and inhibition caused by response competition between target and distractor may be strong. The results showed that the effect of a set size of stimuli was more dominant in the word-word task, and was not exhibited in the picture-word task and picture-picture task. It was suggested that different cognitive process might underlie these tasks.