This study examines the relationship between personal differences and use of Facebook by pre-service teachers and compares the results from Turkey and the U.S. In addition to the "big five" personality traits, attitude, motivation, and specific motives are also examined among personal differences. The sample consisted of 762 pre-service teachers who use Facebook. Regression analyses conducted on the data collected from the two countries revealed, firstly, that personal differences are associated with Facebook use. Secondly, however, the associations differed remarkably between the two countries. Even individuals with the same personal characteristics used Facebook differently between the countries. On the other hand, in both countries a strong privacy concern and a perceived 'unrealness' emerged as negative factors. Individuals who consider social networking services as a place to pass time are avid users in both countries, as well. Furthermore, agreeableness and friendship related to Facebook use were not factors in either country.