<p>This study aims to analyse the prescription of medication for attention-deficit/hyperactivity disorder (ADHD) in children and adolescents, by age group and gender, before and during the COVID-19 pandemic, as well as the impact of government policies during this period. This study was a retrospective cohort analysis using data from the Portuguese national prescription database and included all children and adolescents aged 5–19 years. We conducted an interrupted time series analysis, modelled using a seasonal autoregressive integrated moving average (SARIMA) approach, to evaluate the impact on prescription medications while considering two intervention points resulting from government policies: March 2020, marking the start of strict anti-pandemic measures, and May 2021, marking the beginning of their easing. Following the start of strict anti-pandemic measures, from March 2020 to May 2021, a 9% lower prescription rate than expected was observed, while from June 2021 to December 2023, the prescription rate was greater than expected (+ 32%, with a peak of + 41% in children 5–9 years old) and more pronounced in girls. <i>Conclusions</i>: These findings highlight the complex impact of the pandemic on different age groups and between genders on the prescription of ADHD medicines.<Table Float="No" ID="Taba"> <tgroup cols="1"> <colspec align="left" colname="c1" colnum="1" /> <tbody> <row> <entry align="left" colname="c1"> <p><b>What is Known:</b></p> <p>• <i>ADHD medications are considered effective and have been increasingly prescribed to children and adolescents in recent years.</i></p> </entry> </row> <row> <entry align="left" colname="c1"> <p><b>What is New:</b></p> <p>• <i>Following the COVID-19 pandemic, the increase in ADHD medication prescriptions exceeded expected trends.</i></p> <p>• <i>Stratification by age group and gender revealed gender differences, with a more pronounced rise in prescriptions observed among girls.</i></p> </entry> </row> </tbody> </tgroup> </Table></p>