The Improving Young People's Mental Health Services forum was set up by the relatives of 15-year-old Oliver Edwards-Cavill, who took his own life in 2008.
Both Pembrokeshire council and Hywel Dda Health Board were due to be on the panel, but both were unable to attend.
Hywel Dda said it was down to staff sickness.
The headmistress of Greenhill  School and representatives from Pembrokeshire College, Age Cymru and the mental health charity Hafal were among those to attend the event in Pembroke Dock.
Some audience members were frustrated by the council and health board's absence from the panel.
Libby Ryan-Davies, director of Mental Health and Learning Disabilities for Hywel Dda University Health Board, said it was down to staff sickness and despite attempts, they were unable find a replacement.
She said a staff representative participated as an audience member.
Pembrokeshire council has been asked to comment.
Some of the issues discussed were the safeguarding of children in schools and a reduction of local authority services around mental health.
Oliver's aunt Suzannah Palmer, hoped the forum would stop another family "having to bury their child".
Oliver's cousin, London barrister Matthew Watkins, told BBC Wales that since his death, they have read about other young people taking their lives.
"Over the past few years, there have been a number of children who have taken their lives and from what we have seen there has not been a huge amount of support, he said.
"We want to go about it the right way.
"We want to engage with all the services because we are not mental health specialists; we need to be informed where we can direct our efforts."
Pembrokeshire council said there are "a range of universal school-based support available to secondary school pupils in Pembrokeshire, as well as targeted support provided in school by outside agencies".
There is also "specific support for complex young people", the council added.
Around 50 people met in Pembrokeshire on Friday to discuss concerns about the mental health of young people.