Girls outnumber boys almost two-to-one in getting treatment for drug or alcohol-related illnesses in 2020.
Over 900 children - with 589 girls and 325 boys - were treated for drug or alcohol poisoning, mental health disorders due to subtance misuse, and other illnesses.
686 children were aged between 10 and 17, and 228 were under nine years old.
Consultant paediatrician Ciara Martin, from Children's Health Ireland, says the figures are only the tip of the iceberg.
"I would think that there are a large number of children in that age group out there who have alcohol and toxic effects of alcohol in their system but are brought home and supported during the night, and kept at home.
"Whereas the ones who are vomiting or are unconscious or have other injuries - or are hypothermic if found outside - are the ones that come into hospital."
259 were treated in the four children's hospitals in Dublin.
185 were inpatients in the South/Southwest Hospital Group, with almost 99 females between the age of 10-17, which includes University Hospital Waterford and South Tipperary General Hospital.
While there were 138 inpatients across the Ireland East Hospital Group, which includes St Luke's General Hospital in Kilkenny and Wexford General Hospital.
