Psychotic disorders (PDs) and attention-deficit hyperactivity disorder (ADHD) are frequently comorbid. Clinicians are often reticent to treat ADHD in patients with psychosis, fearing that psychostimulants will worsen psychotic symptoms. Advances in neurobiology have challenged the simplistic dichotomy where PD is considered a disorder of high dopamine (DA), treated by DA antagonists, and ADHD a disorder of low DA, treated by DA agonists. In our paper, we review the literature on comorbid ADHD and psychosis. Treating ADHD with psychostimulants may be considered in patients with PD who have been stabilized with antipsychotics (APs). Not treating ADHD may have consequences because ADHD may predispose patients to drug abuse, which further increases the risk of PD. Nevertheless, more systematic studies are needed as there remains some uncertainty on the combined use of APs and psychostimulants in comorbid PD and ADHD.