Almost 600 calls, texts and online messages were answered by Childline, a 24-hour support line for under-18s, over the last three days.
The Irish Society for the Prevention of Cruelty to Children (ISPCC), who operate the Childline service, said that drink and drug abuse were common concerns among children who contacted the charity on Christmas Day.
Other issues raised by children who recently contacted Childline included family relationships, and sex or puberty.
Over 70 volunteers were involved in operating the support line over the Christmas period.
John Church, chief executive at the ISPCC, said tensions within families have continued since the onset of the pandemic.
"[The] top issues was same as last year, which is all about family relationships," Mr Church told Newstalk radio.
"And then that really is impacting on their mental health, and emotional health.
"And we've seen this anxiety as well continue, during Covid and post Covid, anxiety amongst children and young people, that has certainly continued throughout the year," Mr Church said.
In a statement, Mr Church also added: "“Many children and young people in Ireland felt lonely, stressed and upset this Christmas. Their feelings were exacerbated as they saw families and friends celebrating together and it’s not like that for them.
"They turned to Childline for a listening ear and a supportive voice to hear them.
Mr Church paid tribute to the work of volunteers, and the public support for the work of Childline and the ISPCC.
"On behalf of all the children and young people who Childline supports, we would like to say thank you to the people of Ireland for all they do to help keep the service here 24 hours a day, every day. We are sincerely grateful to you for helping to ensure children and young people have someone to turn to, always," he said.
