This is what wikipedia says:
Research suggests that pedophilia may be correlated with several different neurological abnormalities, and often co-exists with other personality disorders and psychological pathologies. In the contexts of forensic psychology and law enforcement, a variety of typologies have been suggested to categorize pedophiles according to behavior and motivations. [12]
Here is the link to the full article http://en.wikipedia.org/wiki/Pedophilia
Since it cannot be cured many states have laws that allow pedophiliacs to be civilly commited after they serve their prison time. This is something I whole heartedly support. Just as we feel no mercy for psychopathic killers neither should we be merciful to pedophiles.