The Early Childhood Inventory-4 (ECI-4) Hyperactivity-Impulsivity (HI) and Inattention (IA) subscales are screeners for attention-deficit/hyperactivity disorder (ADHD). There have been few studies of the screening properties of these subscales, particularly outside the United States. We investigated the classification accuracy of the parent and teacher versions of the HI and IA subscales and the cross-cultural validity of the cutoff values based on norms from a United States sample. The present study was part of the Norwegian Mother and Child Cohort Study. Parents and teachers rated boys (n = 332) and girls (n = 319) with the ECI-4 (mean Age 3.5 years). Interviewers who were blind to the ratings used the Preschool Age Psychiatric Assessment Interview to assign ADHD diagnoses. The ECI-4 HI and IA subscales showed acceptable accuracy in identifying ADHD in boys and girls (areas under the curve ranged from .67 to .85). In a multivariate regression analysis, the parent and teacher HI subscale scores significantly contributed to ADHD identification, but not the IA subscale scores. To achieve the necessary sensitivity to detect children with ADHD, lower cutoff levels than those specified by the United States ECI-4 norms were needed. For screening purposes, the parent and teacher ECI-4 showed acceptable accuracy in identifying preschoolers at risk for ADHD, and it may be sufficient to use the HI subscale scores. The suggested cutoff values provided by the United States ECI-4 norms had limited cross-cultural validity. (PsycINFO Database Record (c) 2019 APA, all rights reserved).