A new report has found some children and young people accessing child and mental health services were left without a follow-up appointment for up to two years.
The report found some children are being "lost" to follow-up care, with no planning, discharge or transition to adult services when they turned 18, or any advice about medication.
The Interim Report, published by the Mental Health Commission, found that in one Community Healthcare Organisation (CHO) alone, there were 140 "lost" cases within the CAMHS team.
These children were described as being "lost" within the system and in some cases, didn't have an appointment for up to two years.
The Interim Report was authored by Dr Susan Finnerty, the Inspector of Mental Health Services.
The report also found evidence that some CAHMS teams were not monitoring antipsychotic medication, in accordance with international standards (there are currently no Irish national standards).
Some children were found to be taking medication without appropriate blood tests and physical monitoring.
John Farrelly, Chief Executive of the Mental Health Commission, said "the Inspector's Interim Report shows clear failings of governance and oversight with no evidence that a national coordinated approach is being taken to caring for children with a mental illness.
"Our core concern should be for the health and welfare of these children and the priority now for the HSE must be identifying and safeguarding the children "lost" to follow-up.
"The Inspector of Mental Health Services has advised the HSE to commence an immediate clinical review of all open cases in all CAMHS teams, with particular focus given to identifying and assessing children who have been lost to follow-up and physical health monitoring of those on antipsychotic medication."