Criminal justice diversion programs have been recognized for their potential to provide positive outcomes for people with serious mental illness by increasing access to community-based treatment services, reducing police contact, reducing time spent in jail, and reducing rates of reincarceration. In pre-booking diversion, police officers that encounter an individual exhibiting symptoms of a mental disorder that is committing a low-level offense are allowed to use their discretion to determine the necessity of arrest. Post-booking diversion occurs after an individual has been arrested and booked for a criminal offense, often a misdemeanor offense. A multisite longitudinal study was conducted to evaluate pre-booking and post-booking diversion programs across the country. The 8 sites conducted baseline interviews with 1,966 subjects--971 diverted and 995 non-diverted. A cross-site questionnaire was developed and used at all sites. The differences found between the pre-booking and post-booking sites indicate that different models of diversion tend to target different populations. Subjects that were diverted at the pre-booking sites were more educated, more involved with employment, and more satisfied with their lives, health, and finances. In general, it appears that post-booking subjects, as a group, are more functionally impaired than those that are diverted at the pre-booking stage. Post-booking programs are characterized by greater supervision by courts and other diversion or case management personnel providing more oversight in the community of offenders at greater risk for offending and for engaging in other negative behaviors. The increased oversight and more directive approach of the post-booking model might be an important variable to the success of the diversion for mentally ill clients with heavy substance use, prior criminal justice involvement, and less robust functioning. 7 tables, 2 notes, 42 references