Thirty to 80% of children with autism spectrum disorder also have symptoms of attention-deficit hyperactivity disorder. Many children with autism spectrum disorder and attention-deficit hyperactivity disorder experience difficulties carrying out goal-directed behaviors, particularly when it comes to inhibiting responses. The aim of this study was to better understand the relative strengths and weaknesses across different measures of inhibition in children with autism spectrum disorder, attention-deficit hyperactivity disorder, autism spectrum disorder + attention-deficit hyperactivity disorder, and children who are typically developing. Inhibition of distracting information, motor responses, response speed, and selections with the potential for greater loss was measured in 155 school-aged children across these four groups. Results indicate that, for children with autism spectrum disorder + attention-deficit hyperactivity disorder, inhibition varied across the different outcomes assessed. Relative to typically developing children, children with autism spectrum disorder + attention-deficit hyperactivity disorder showed greater difficulty inhibiting behavioral responses. Conversely, inhibition of distracting information and strategic slowing of response speed differed between the children with autism spectrum disorder + attention-deficit hyperactivity disorder and those with either autism spectrum disorder or attention-deficit hyperactivity disorder. Avoidance of potential losses did not significantly differ between the four groups. The unique pattern of inhibition abilities shown in the autism spectrum disorder + attention-deficit hyperactivity disorder group suggests the need for special consideration in the context of targeted intervention.