The purpose of the present study is to explore semantic and collocational differences of the two English synonymous adjectives immediate and instant employing the large-scale corpus, WordbanksOnline. Although both immediate and instant are used to communicate that something happens or is done without delay, their usages are different from each other in the following viewpoint: whether the events or actions are intentional or not. First, immediate tends to co-occur mainly with nouns which involves someone’s intention, including comment, action, release, report, and withdrawal. This behavior of immediate indicates that it is used to describe people’s rapid actions or reactions, especially when these are seen as intentional, that is, as a result of a decision. Second, instant is often followed by nouns which express changes in social status, physical condition, or emotion uncontrollable by someone’s intention such as hit, gratification, death, dislike, and celebrity. Therefore, it is typically used to describe events or reactions happening right away which are not a result of someone’s intention or decision but a consequence of something else. Moreover, instant is often used with some nouns, for example, message, access, replay, communication, and camera, resulting in involving someone’s intention. Actions done through these nouns are considered beneficial to someone; therefore, although the actions are intentional, instant can be used when someone gains benefit easily as a result of the actions.