Background: From current theories on the etiology of attention deficit hyperactivity disorder (ADHD), it can be inferred that delay aversion (DA) and deficits in inhibitory control (IC) constitute basic deficits or endophenotypes of the disorder that already occur in the preschool period. This implies an occurrence of the characteristics in unaffected preschoolers with a positive family history of ADHD. Thus, it is hypothesized that preschoolers who are not affected by ADHD but who have first-degree relatives who suffer, or have suffered, from ADHD show deficits in IC and heightened DA in comparison to preschoolers from the general population. Methods: Thirty unaffected preschoolers with a positive family history of ADHD were compared with 30 control children matched with respect to age in months, gender, intelligence, and maternal education level. The groups also did not differ in terms of maternal depressive symptoms and the number of psychosocial family risks. A set of age-appropriate neuropsychological tasks on executive IC (e.g. Puppet Says, Day-Night, relying on Go-NoGo and interference paradigms) and DA (e.g. Snack Delay, Gift Wrap, relying on delay of gratification paradigm) was conducted. Results: Unaffected preschoolers showed significantly higher DA than control children (t(29) = -2.57, p < .008). The result did not change when subclinical ADHD symptoms and symptoms of oppositional defiant disorder were controlled for (F(1,29) = 5.21, p < .031). Differences in IC did not reach statistical significance. Conclusion: The results are compatible with the assumption that DA constitutes a familial vulnerability marker that can be validly assessed in the preschool period. As this is the first study to address this issue in preschoolers, more research is needed to confirm and further analyze the significance of DA assessments specifically at this developmental stage.