The Second National Incidence Studies of Missing, Abducted, Runaway, and Thrownaway Children classified kidnappings as either family or non-family abductions.

Family abduction was defined as the taking or keeping of a child by a family member in violation of a custody order, decree, or other legitimate custodial rights, where the taking or keeping involved some element of concealment, flight, or intent to deprive a lawful custodian indefinitely of custodial privileges.

Non-family abduction was subdivided into "stereotypical kidnappings" which fit the public stereotype of the crime, and legal definition abductions, which are generally short-term forced movement or detention of children to facilitate another crime such as robbery or sexual assault..

Sources: Heather Hammer, David Finkelhor & Andrea J. Sedlak (2002). Children Abducted by Family Members: National Estimates and Characteristics. Juvenile Justice Bulletin–NCJ196466, 1-12. Order #MC17

David Finkelhor, Heather Hammer and Andrea J. Sedlak (2002). Nonfamily Abducted Children: National Estimates and Characteristics. Juvenile Justice Bulletin–NCJ196467, 1-16. Order #MC19