Scores of under-18s were admitted to adult psychiatric wards last year, a watchdog said today.
The Mental Welfare Commission for Scotland said a total of 134 young people were sent to the wards in 2007/2008.
While this represented a 24% fall on such admissions compared with the previous year, the commission said it was still concerned.
A total of 142 under-18s were admitted to non-specialist services, a figure which includes those sent to adult psychiatric wards.
For 21 of them, there was no access to specialist psychiatric services.
A similar number also failed to get the education support they were entitled to.
The figures were disclosed in the watchdog's annual report, Wrong Place, Wrong Time?
The commission called on health boards to fulfil their legal duty to provide appropriate services for under-18s with mental health problems.
It also urged the Scottish Government to review adolescent mental health services across the country.
Commission director Dr Donald Lyons warned a lack of specialist care for young people with psychiatric problems increased the risk of social exclusion and further mental health issues.
He said: "Being admitted to an adult ward as a young person means that you are less likely to continue to access education, less likely to receive specialist clinical input and less likely to have an allocated social worker.
"Without specialist assessment and care plans that include social and educational support, the risk of long-term social exclusion increases, as does an individual's risk of experiencing further serious mental health problems in future."
He added: "It might not always be possible or appropriate for a young person to be admitted to a specialist ward but - whatever the setting - he or she should be guaranteed specialist care and treatment."
The commission report highlighted the example of a 16-year-old girl, known as Ms Y.
She received care and treatment on an adult ward from December 2006 to August 2007.
During her admission to hospital she received no specialist care, despite a mental health tribunal order that her health board should ensure this was provided.
Kathleen Marshall, Scotland's commissioner for children and young people, backed the calls for young people to receive appropriate treatment.
She said: "It's vital that young people with mental welfare care needs can access treatment and services that are appropriate.
"This means reducing admissions to adult wards and providing more specialist support for those who are admitted to adult wards."