The goal of the study was to examine baseline characteristics-child gender, IQ, age, internalizing problems, symptoms of hyperactivity/impulsivity (HI), oppositional defiant disorder, and sluggish cognitive tempo, and parent income, education, attention deficit/hyperactivity disorder (ADHD) severity, and anxiety/depression (A/D)-associated with response to behavioral treatments for ADHD, predominantly inattentive type. We employed data from 148 children (M = 8.7 years), 58% male, and 57% Caucasian in a randomized clinical trial. Positive treatment response was defined as (a) 5 or fewer inattentive symptoms and (b) a decrease of at least 3 inattentive symptoms from baseline to posttreatment. Child HI, parental A/D, and child IQ were associated with positive response, as follows: Child HI had a main effect in which it was negatively associated with treatment response (36% with 2 or more HI symptoms were positive responders vs. 59% of those with 1 or no symptoms) that was qualified by parental A/D and child IQ. When children had 2 or more symptoms of HI and higher parental A/D, positive response rate was low at 25%; when children had 2 or more symptoms of HI, low parental A/D, and an IQ of 105 or higher, positive response rate was 85%. Furthermore, the group with the poorest response rate (25%) had parents who self-reported greater ADHD severity, and the group with a relatively good rate of positive response (59%) had the lowest number of oppositional defiant disorder symptoms. Likelihood of positive response to our behavioral treatment for ADHD-I is dependent on child and parent factors.