(British: Nappy fetish)
Diaper fetishism, or diaperism, is a paraphilia in which a person feels a strong desire to wear or use diapers, usually without physiological necessity. It is differentiated from infantilism in that those of the latter category are also focused with returning to babyhood in ways other than by wearing diapers. The popular term for diaper fetishists is "diaper lover." Diaper fetishism is a type of sexual fetishism, which is one of many paraphilias.
As of 2007, little analysis of this paraphilia has been reported in medical literature. 
Diapers in paraphilias
Diapers (nappies) are often utilized by a wide range of paraphilias.
Diaper fetishes are often associated with paraphilic infantilism. Similarly, diaper lovers (DLs for short) are often associated with the adult babies (ABs). While there is some commonality, they are not identical. The majority of diaper lovers do not engage in any kind of babyish activities and only solely are interested in diapers. However, about four in ten diaper lovers also consider themselves adult babies, so they are sometimes collectively referred to as AB/DLs.These desires are not related to pedophilia or infantophilia in any way. Inside the AB/DL communities, a sharp distinction is observed. Most of these communities will actively expel child molesters.
Main article: Garment_fetishism#Latex.2FPVC
Some rubber and plastic fetishists have an affinity for diapers and rubber pants.  In this case of diapers, this attraction would be to the crinkly plastic of disposable diapers. In the case of cloth diapers, it would be towards the latex or pvc of the pants worn over them.
Diapers are sometimes used during prolonged bondage sessions, not only as a method to control and shame the submissive partner, but also to allow longer periods of bondage. In Total Power Exchange, diapers are sometimes utilized for the dependency they represent of the wearer on their master to be checked and changed.
Those practicing a diaper fetish often form groups. For example, in schools and such. (Though most high-schoolers are embarressed about their fetish, if there is a group it is easier to admit.) Many times, these people have no wish to become babyish or even to put the diaper to practical use, it is just an attractive garmet like some find latex or red panties. The groups often decide these preferences more so than individuals. Sometimes rules are established. Like, it is shameful to change your own diaper. Or, diapers should be at least somewhat publicly visible.
Omorashi (オモラシ / おもらし / お漏らし, Omorashi?) is a fetish subculture recognized predominantly in Japan, in which participants experience arousal from having a full bladder or a sexual attraction to someone else experiencing the feeling of a full bladder. For such fetishists, climax usually coincides with the moment of relief and embarrassment experienced when the desperate individual loses bladder control. Some subsets of omorashi fandom utilize diapers, in which case it is referred to as "omorashi omutsu," or less commonly called "omorashi oshime," both of which translate as "to wet oneself in a diaper."
Preferences in diaper fetishism
Like many fetishes, personal preference plays a large role in which communities the fetishist will identify with. In diaper fetishism, one of the primary divisions of preference is whether or not the diapers are used for their intended purpose, and if so, to what degree.
Many diaper lovers gain arousal from "wetting" or urinating in their diapers. A smaller number gain the same arousal from using the diaper to "mess" or defecate. Some fetishists do not use their diapers at all. They may find such practices unappealing or they might not want to deal with the cleanup. Others may become aroused by wearing in public; still others prefer the security of wearing only in private.
Many diaper lovers choose to wear in both public and private, using their diapers as intended and never visiting the toilet. Though for a large group this embodies the full spirit of the fetish, others have found that their enjoyment of wearing diapers diminishes rapidly when the need to wear diapers is always present.
Another preference might be cloth or disposable. Disposables have become increasingly popular in recent years due to better availability and ease of clean-up, but many diaper lovers who were babies in the era of washable cloth diapers tend to prefer washables as adults. This makes a strong case for the idea that the psychology of diaper fetishism is a form of anaclitism.
1. ^ Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Washington, DC, American Psychiatric Association, 2000, pg 566-570 (4th ed. TR)
2. ^ Pate J.E., Gabbard G.O. (2003). Adult baby syndrome Am J Psychiatry 160:1932–1936
3. ^ Malitz S, (1966).Another report on the wearing of diapers and rubber pants by an adult male. Am J Psychiatry 122:1435–1437
4. ^ Thomas John Speaker, Psychosexual Infantilism in Adults: The Eroticization of Regression. Columbia Pacific University. pg 83. Available from: DPF, Sausalito, CA 94965.
5. ^ Section 10 - Into the Future Retrieved 2002 from http://www.geocities.com/SouthBeach/Island/5861/ds3_s10.txt, now mirrored at http://web.archive.org/web/20010424192400/www.geocities.com/SouthBeach/Island/5861/DS3_S10.txt
6. ^ Watson, J. (2005, June 9). Baby Man, Thomas John Speaker, Psychosexual Infantilism in Adults: The Eroticization of Regression. Columbia Pacific University. pg 78. Available from: DPF, Sausalito, CA 94965.
7. ^ Arndt, William B., Jr. (1991). Gender Disorders and the Paraphilias, International Universities Press, pg 394, ISBN 0-8236-2150-2.
8. ^ Gilstrap, P. (1999, March 7-11). The Diapers They Are a-Changin'. The New Times Los Angeles. Available from DPF and the website of the interviewee, Mike A.
9. ^ Understanding.infantilism.org
10. ^ Arizona Power Exchange News, April 2006, Volume 18, Issue 4
11. ^ Thomas John Speaker, Psychosexual Infantilism in Adults: The Eroticization of Regression. Columbia Pacific University. pg 81. Available from: DPF, Sausalito, CA 94965.