The Crisis intervention team model (CIT) is possibly the most well known and widely adopted model to improve police response to persons with mental illness. A primary goal of CIT programs is to divert individuals with mental illness from the criminal justice system to mental health services. In this paper we examine the effectiveness of fielding CIT trained and supported officers for influencing call outcomes using data from patrol officers (n = 112) in four Chicago Police districts. Results from regression analysis indicate that CIT certified officers directed a greater proportion of persons with mental illness to mental health services than their Non-CIT certified peers. CIT did not have an immediate effect on arrest. Moderator analysis indicates that CIT had its biggest effect on increasing direction to services and decreasing "contact only" among officers who have a positive view of mental health services and who know a person with mental illness in their personal life. Additional moderators of the CIT effect on call outcomes include level of resistance and the presence of a weapon. Findings from this study have important implications for policy, practice and future research.