Purpose <p>The aim of the study is to examine (i) if young children with a family history of autism and/or ADHD differ on executive functions and deferred gratification in comparison to peers with no family history of autism or ADHD, (ii) the specificity of these domains in relation to early-life autistic and ADHD symptoms and adaptive functioning, and (iii) if deferred gratification and strong EF skills may function as protective factors in the association between symptoms and adaptive behaviour.</p> Methods <p>A total of 77 infant siblings at 3&#xa0;years of age with a family history of autism only, autism and co-occurring ADHD, or no family history of these conditions (FH-TL) were assessed on behavioural lab-tasks (EF and deferred gratification), parent-rated adaptive behaviour using Vineland, and clinician ratings using ADOS-2 (autistic symptoms) and ADHD DSM-5 symptom rating scale (ADHD RS).</p> Results <p>Group comparisons showed that FH-autism and FH-autism + ADHD groups received lower scores on common EF, but not on deferred gratification in comparison to the FH-TL group. Lower levels of deferred gratification related to autistic symptoms, while lower level on EF was specific to ADHD symptoms. Finally, deferred gratification moderated the association between autistic symptoms and adaptive behaviour, in that stronger ability to defer gratification attenuated the association between autistic symptoms and adaptive functions.</p> Conclusions <p>These results are in line with the idea that strong ability to inhibit and defer gratification may act as a protective factor for children with a family history of autism and/or ADHD pointing to affective aspects of EF as particularly important.</p>