Purpose: To examine remote learning practices and difficulties during initial stay-at-home orders during the COVID-19 pandemic in adolescents with and without ADHD. Methods: Participants were 238 adolescents (132 males; 118 with ADHD) ages 15.64-17.99 years and their parents. Adolescents and parents completed questionnaires in May/June 2020 when in-person schools were closed in the United States. Results: Twenty-two percent of families incurred financial costs to support remote learning, and only 59% of school-based services received prior to COVID-19 continued during COVID-19 remote learning. Adolescents with ADHD had fewer routines and more remote learning difficulties than adolescents without ADHD. Parents of adolescents with ADHD had less confidence in managing remote learning and more difficulties in supporting home learning and home-school communication. Thirty-one percent of parents of adolescents with ADHD with an Individualized Education Program (IEP) or receiving academic accommodations (504 Plan) reported remote learning to be very challenging, compared to 18% of parents of adolescents with ADHD without an IEP/504 Plan and only 4% of parents of adolescents with neither ADHD nor an IEP/504 Plan. Fewer adolescent routines, higher negative affect, and more difficulty concentrating because of COVID-19 were each associated with greater adolescent remote learning difficulties only in adolescents with ADHD. Conclusions: This study provides initial findings of the nature and impact of remote learning during the COVID-19 pandemic. It is imperative for schools and communities to provide the necessary supports to adolescents, particularly those with mental health and/or learning difficulties, and to their parents. Implications and Contributions: The start of the COVID-19 pandemic included the near-universal closing of schools. This study describes the remote learning practices, continuation of school services, financial burden to families, and remote learning difficulties in adolescents with and without ADHD when initial stay-at-home orders were in place in the United States. [This paper was published in "Journal of Adolescent Health" v67 n6 p769-777 2020.]