Currently, diagnostic criteria for ADHD mainly reflect behavioral symptoms, neglecting internal phenomena like mind-wandering. Recent studies found that mind-wandering explains impairment beyond ADHD symptoms in adults. To better capture ADHD-related impairment in adolescents, we aimed to elucidate whether mind-wandering is associated with impairments that are prevalent in adolescents (i.e., risk-taking behavior, homework problems, emotional dysregulation, and general impairment) beyond ADHD symptoms. Furthermore, we sought to validate the Dutch translation of the Mind Excessively Wandering Scale (MEWS). We assessed a community sample of 626 adolescents on ADHD symptoms, mind-wandering, and the impairment domains. The Dutch MEWS had good psychometric properties. Mind-wandering was linked to general impairment and emotional dysregulation beyond ADHD symptoms, but was not linked to risk-taking behavior and homework problems beyond ADHD symptoms. Internal psychological phenomena such as mind-wandering may add to the behavioral symptoms of ADHD in explaining part of the impairment that adolescents with ADHD characteristics experience.