Attention-deficit/hyperactivity disorder (ADHD) is a prevalent disorder of childhood with a strong genetic contribution. Recently there has been a massive increase in research across multiple fronts, including genetics, neuropsychology and neuroimaging, with impressive gains made. Here, we review the extant literature on the genetic correlates of cognitive deficits in ADHD, focusing on deficits of sustained attention, heightened reaction-time variability and asymmetries of directed spatial attention. The new era of multidisciplinary research means that links can be forged across multiple levels (e.g., gene-cognition) with potentially important implications for treatment. In this review, we highlight how gene-cognition linkages in ADHD might be profitably used to suggest novel approaches to monitoring stimulant-medication responses, as well as strategies for targeting cognitive remediation techniques towards particular subgroups of children and adults with ADHD.