Nowadays, computer-mediated communications such as chatting and e-mail are widely used in younger generation. It has been known that the communicating words used by on-line users (so-called netizens) are quite different from those used by ordinary people. That is, the words are generally characterized by shortened, mimetic and onomatopoeic words, and the netizens also use various types of emoticon expressed like signs or symbols. This can cause some orthographic as well as cultural problems. This paper investigates some statistical data in PC-based communications, analyzes the general characteristics, and provides some explanations.