The scales are set up for convenience into four broad categories, bringing together those having related implications. The underlying logic of the categories is interpretational, not factorial. The four categories are not necessarily intended to constitute psychometric entities (California Psychological Inventory Scales, 2009). The items on the inventory produce scores for 18 different scales, which are divided into four classes. These classes include: measures of poise, ascendancy, self-assurance and inter-personal adequacy; measures of socialization, responsibility, intra-personal values, and character; measures of achievement potential and intellectual efficiency; and measures of intellectual and interest modes (California Psychological Inventory Scales, 2009).

These two tests are very different in what they are used for. The MMPI-2 is basically used to diagnose and treat mental illnesses in adults, while the CPI is used for those 13 and over who are considered normal in order to evaluate interpersonal behavior and social interaction....

It would be highly unlikely that these tests would be used in the same case because of the fact that each measures something different. The CPI was created in a very similar manner to the MMPI-2 and in fact shares 194 of the same questions. But it is different from the MMPI, which centers on maladjustment or clinical diagnosis, while the CPI was created to assess the everyday folk-concepts that ordinary people use to describe the behavior of the people around them (Aiken, 2004).
References

Aiken, L.R. (2004) Psychological Testing and Assessment. New York: Allyn and Bacon.

California Psychological Inventory Scales. (2009). Retrieved November 17, 2009, from Kids IQ

Test Center Web site: http://www.kids-iq-tests.com/California-Psychological-Inventory.html

Van Wagner, Kendra. (2009). The Minnesota Multiphasic Personality Inventory - MMPI-2.

Retrieved November 17, 2009, from About.com Web site:

http://psychology.about.com/od/psychologicaltesting/a/mmpi.htm