Youth mental health referrals double in four years
The number of children and young people referred to mental health services has more than doubled since 2010.
In December 2010, 1,200 under-18s were waiting for their first outpatient appointment, rising to 2,500 in December 2014.
Health Minister Mark Drakeford said the service faced "ever-increasing demand".
It comes after a report by assembly members last year found mental health services for children and young people in Wales could not cope with demand.
NHS bosses, experts and social services staff from across Wales are meeting in Cardiff on Thursday for a conference to discuss the future of the service.
The Welsh government said it had ring-fenced mental health spending and increased the budget from £389m in 2009-10 to £587m in 2014-15.
But Mr Drakeford stressed that after examining the issue, it was found that "far too many referrals" to child and adolescent mental health services did not require that specialist service.
"With this goes a great deal of frustration for those children, young people and their families who learned that they have been sent down a route, which will not best meet their needs," he added.
A report by the Children, Young People and Education committee in November found the number of youngsters referred to the Children and Adolescent Mental Health Services (CAMHS) had doubled between 2010 and 2014.
The Welsh government said it was already tackling the issue, but members said they had "serious concerns" and asked if enough money was being provided for the service.