In children and adults with epilepsy, it is important to be aware of and diagnose common comorbidities that may have a large impact on quality of life. Comorbid neurodevelopmental disorders include intellectual disability, autism, and attention deficit hyperactivity disorder (ADHD). Depression and anxiety are common findings, and also the risk of psychosis is increased. The medication used to treat these comorbidities is found to be effective with little risks of seizure exacerbation, i.e. medication with methylphenidate, selective serotonin reuptake inhibitors (SSRIs) and second generation neuroleptics. However, for every combination of antiepileptic drugs with new medication, the possibility of drug interactions should be kept in mind. Transition from childhood to adult medicine must include adequate treatment and follow-up of comorbid conditions.