Most would agree that child pornography constitutes sexualized pictures that involve children; however, what is meant by "sexualized" can vary depending on whether a legal or the more subjective perspective of the adult with a sexual interest in children is taken. Legal definitions tend to emphasize obscene or sexual content as an essential quality of the images, but such definitions may vary depending on the legislature within a given country. This is a particular problem in relation to the Internet, where cultural, moral, and legal variations make it difficult to define "pornographic" in such a global society. Based on the COPINE Project at the Department of Applied Psychology, University College Cork (England), this paper presents 10 levels of a typology of pictures of children according to 10 levels of severity of sexual involvement. In discussing Internet sources of child pornography, this paper notes that a major source for both text and images is the Usenet Newsgroups. There are some 30,000 such groups on the Internet, covering a wide range of subjects; pedophiles use some of these newsgroups to communicate with each other and to ask advice about computer-related problems. Bulletin Board Systems are similar to newsgroups, but with more real time involvement. The World Wide Web is another source of child pornography. It is now relatively easy to create Web pages, and features built into Web browsers enable users to capture content created by other people with a minimum of effort. Although those who access child pornography through the Internet evidence many similarities with other child sex offenders, they also demonstrate varying measures of "functional addiction," such as salience, mood modification, tolerance, withdrawal symptoms, and conflict and relapse. This is an important consideration in the development of both appropriate assessment and treatment programs for offenders. Training for law enforcement and other professionals must address the evidential issues that relate to the pictures, with emphasis on tracing the chain of postings and seeing the picture content as evidential forensic material. This requires knowledge of the behavior of downloaders and the language they use. Suggestions are also offered for how Internet Service Providers might assist in preventing the display of child pornography through the Internet. 21 notes