During the COVID-19 pandemic, countries imposed (partial) lockdowns that reduced viral transmission. However, these interventions may have unfavorable effects on emotional and psychological well-being. The aim of this study was to quantify possible adverse effects of the COVID-19 pandemic on psychological wellbeing in children and adolescents. Hospital admission data between January 2017 and September 2021 from eight general hospitals in the Netherlands was collected, comparing the incidences of sub-categorized psychological diagnoses, more specifically eating disorders, intentional intoxications, accidental intoxications, and excessive crying, before (2017–2019) and during the pandemic (2020–2021). Data was summarized per month and per year, and the years 2020 and 2021 were compared to 2017–2019. The relative increase or decrease in diagnoses since the start of the pandemic was calculated. Overall pediatric hospital admissions decreased with 28% since the start of the pandemic. Non-infectious diagnoses showed a decrease of 8%. Of these non-infectious diagnoses, overall psychosocial admissions were increased (+ 9%), mostly caused by an increase in admissions for eating disorders (+ 64%) and intoxications in adolescents (+ 24%). In addition, the proportion of admissions due to psychosocial diagnoses increased post-pandemic (6% vs 4%, p < 0.001). Overall admissions for intoxications in children (− 3%) and excessive crying (− 1%) did not increase, although peaks in incidence were found at the start of the second lockdown. Conclusion : During the COVID-19 pandemic, admission rates for eating disorders and intentional intoxications showed a substantial increase, indicating a high burden of pediatric psychiatric diseases. What is Known: • The COVID-19 pandemic has had an impact on psychosocial wellbeing in children and adolescents. What is New: • There was an increase in admissions due to psychosocial problems in the Netherlands in the period after the pandemic. • This was mainly caused by an increase in crisis admissions due to eating disorders and intoxications in adolescents. Supplementary Information The online version contains supplementary material available at 10.1007/s00431-022-04773-5.