Dissociation involves a variety of clinical concepts, and some disorders are also similar to but not the same as dissociation. Dissociative disorder is considered to be a pathological phenomenon based on a psychological mechanism. Accurate diagnosis is very important to ensure that patients receive adequate treatment, although such consideration is not unique to dissociative disorder. Accordingly, there is a need to carefully distinguish dissociation from other disorders. In this article, we outline a number of dissociative and dissociative-like states from the symptoms of amnesia, depersonalization and switching. In particular, we highlight the differences between transient global amnesia and dissociative amnesia, and imaginary companions and dissociative alter personality. Additionally, as the symptoms of conditions such as dissociative amnesia and dissociative identity disorder are easily confused, we also made efforts to organize them.