Adopted children often struggle with their cultural identity as teenagers, according to a charity providing adoption support.
After Adoption aims to raise awareness of the difficulties faced by adoptees at a conference in Cardiff on Tuesday.
In 2010 around 5,162 children were in the care of local authorities in Wales, with 229 adopted from care.
The charity says the complex issues and emotions involved in adoption need to be understood.
Merrill Roberts, After Adoption's service manager for south and west Wales, said: "Knowing where you come from and who your birth parents were is a fundamental building block in terms of establishing who you are and who you will become.
"For adopted children quite often there are chunks missing.
"The conference will look specifically at issues around contact and identity, with international speakers who will bring a lot of knowledge and insight to these issues."
Inge Hansen is an American documentary film maker whose adopted son, now seven, was born in Haiti and has known he was adopted since he was very young.
She said: "He is quite aware of his background - as much as we know about it.
"He will have pieces missing that we probably won't be able to supply to him because we don't know who his birth parents are and it would be pretty impossible for us to find that out.
"We talk a lot about Haiti as we want to make sure that he understand where he is from- it is a part of his life - but we also don't try to get him to address it all the time."
The conference, Contact and Identity in Adoption, is at the Wales Millennium Centre, Cardiff.