Objective: To examine differences across a community mental health system and a private managed care system in the accuracy of a warning system designed to identify youth at risk for deterioration in mental health services. Design: Longitudinal outcome data from the Youth Outcome Questionnaire (Y-OQ) were examined using multilevel modeling for 2,310 youth ages 4–17 who received outpatient treatment. Results: The warning system correctly identified 69% of cases that ultimately ended in deterioration in the community mental health setting, compared to 61% in the managed care setting. The overall hit rate (overall accuracy in classifying cases as deteriorators/non-deteriorators) was the same in the two settings (75%). Conclusions: Results are consistent with previous research demonstrating that patient-focused warning systems can be reasonably accurate in identifying youth cases at risk for treatment failure. © 2011 Wiley Periodicals, Inc. J Clin Psychol 67:1–17, 2011.