Parent education is an effective and relatively cost efficient approach for reducing child behavior problems. Research, however, suggests that the effectiveness of parent education is mitigated by parent attendance and parent implementation of intervention strategies. That is, low attendance at parent education sessions is associated with limited intervention effects. Therefore, it is critical to identify strategies to enhance parent engagement. A previous pilot randomized controlled trial of a parent education program (Behavioral Parent Education; BPE, specifically Promoting Engagement for ADHD pre-Kindergartners \[PEAK\]), found that both face-to-face (F2F) and online BPE resulted in high levels of parent engagement and child behavior improvements. However, results need to be replicated in a full scale efficacy trial with a larger, diverse sample to provide more reliable estimates of relative effect sizes for parent and child outcomes and to evaluate the extent to which parent and child behavior changes are maintained after BPE has ended. In the current randomized controlled trial, the investigators intend to apply What Works Clearinghouse group design standards to examine the efficacy of two forms of delivery of BPE (F2F and online) relative to a wait-list control condition in a sample of 180, 3- to 5-year old children with clinically significant symptoms of ADHD. The objective is to: (a) extend findings from the pilot investigation to a large, diverse sample; (b) examine maintenance of effects; (c) identify moderators and mediators of treatment outcome, especially the degree to which these may differ for F2F vs. online treatment delivery; and (d) assess cost and cost-effectiveness of the two PEAK delivery formats.