From Wiki: http://en.wikipedia.org/wiki/Child_sexual_abuse#Offenders
Early research in the 1970s and 80s began to classify offenders based on their motivations and traits. Groth and Birnbaum (1978) categorized child sexual offenders into two groups, "fixated" and "regressed." Fixated were described as having a primary attraction to children, whereas regressed had largely maintained relationships with other adults, and were even married. This study also showed that adult sexual orientation was not related to the sex of the victim targeted, e.g. men who molested boys often had adult relationships with women.
Later work (Holmes and Holmes, 2002) expanded on the types of offenders and their psychological profiles. They are divided thus:
* Situational - does not prefer children, but offend under certain conditions.
o Regressed - Typically has relationships with adults, but a stressor causes them to seek children as a substitute.
o Morally Indiscriminate - All-around sexual deviant, who may commit other sexual offenses unrelated to children.
o Naive/Inadequate - Often mentally disabled in some way, finds children less threatening.
* Preferential - has true sexual interest in children.
o Mysoped - Sadistic and violent, target strangers more often than acquaintances.
o Fixated - Little or no activity with own age, described as an "overgrown child."
More information about true pedophiles: