Objective: The two-parameter logistic model (2PLM) was used to evaluate the psychometric properties of the inattention (IA) and hyperactivity/impulsivity (HI) symptoms. Method: To accomplish this, parents and teachers completed the Disruptive Behavior Rating Scale (DBRS) for a group of 934 primary school-aged children. Results: The results for the discrimination parameters showed that all the IA and HI symptoms for both groups of respondents were generally good for discriminating those with and without IA and HI, respectively. For virtually all symptoms, their threshold values showed endorsement of the symptoms when the underlying trait levels were at least 1 to 1.5 "SD" above the mean. The item information function values for most symptoms indicated reasonable reliability from around the mean trait levels to moderately high trait levels. Conclusion: These findings indicate good discrimination and reliability for parent and teacher ratings of the DBRS for identifying children with relatively high levels of the ADHD symptoms. (Contains 2 tables and 5 figures.)