OBJECTIVE The authors examined parent-of-origin effects in transmission of ADHD and neuropsychological functioning. Proof of these effects can identify more etiologically homogeneous ADHD subgroups and facilitate genetic studies. METHOD The authors included 238 ADHD and 147 control families. ADHD in children was assessed using parent and teacher ratings, while parents completed self-reports. Children were assessed with neuropsychological paradigms measuring IQ, motor, timing, and executive functions. RESULTS Paternal and maternal ADHD were equally positively related to ADHD in offspring. Paternal ADHD was related to poorer time reproduction in offspring and to lower verbal and total IQ in daughters. Maternal ADHD was related to poorer inhibition and motor control in offspring. No mediating effects of neuropsychological functions were found between parent and offspring ADHD symptoms. CONCLUSION Neuropsychological functions may be more sensitive to parent-of-origin effects than ADHD symptoms and possibly useful in detecting the transmission of different gene-brain network pathways depending on parental sex.