Simple Obsessional:
A prior relationship exists between the victim and the stalker which includes the following:
Acquaintance, neighbor, customer, professional relationship, dating, and lover
The stalking behavior begins after either:
The relationship has gone “sour”, or
The offending individual perceives some mistreatment
The stalker begins a campaign either to rectify the schism, or to seek some type of retribution


Erotomania:
Based on the Diagnostic Statistical Manual, 4th ed. (DSM-IV, 4th ed.)
The central theme of the delusion is that another person is in love with the individual
The delusion often concerns idealized romantic love and spiritual union rather than sexual attraction — “a perfect match”
The object of affection is usually of a higher status and can be a complete stranger
Efforts to contact the victim are common, but the stalker may keep the delusion a secret
Males, seen most often in forensic samples, come into contact with the law during misguided pursuits to “rescue” the individual from some imagined danger. Females are seen most often in clinical samples


Love Obsessional:
Similar to the erotomanic individuals:
The victim is almost always known through the media.
The delusion that the victim loves them may also be held
The erotomanic delusion is but one of several delusions and psychiatric symptoms — this individual has a primary psychiatric diagnosis
These individuals may be obsessed in their love, without having the belief that the target is in love with them
A campaign is begun to make his/her existence known to the victim