Local authorities have been hesitant to refer children and adoptive families to the register, which was set up last year in a bid to speed up and increase adoptions, due to data protection concerns.
The Herald understands only 18 of the country's 32 authorities have signed up to the scheme following confusion over who is responsible for confidential information at different stages of the process.
The Scottish Government, which funded the register for its first three years at a cost of almost £300,000, says the issues have now been addressed. However, adoption campaigners said that the slow progress was frustrating.
Fiona Lettice, Scotland development manager for Adoption UK, a charity that represents adoptive families, said: "It's really frustrating that local authorities have been slow to join up. There are children languishing in the care system and we should be using any way that we can to find families for these children.
"There's been a problem with data protection and some councils were worried about signing up, but as far as I understand, this has been resolved and there is now a data-sharing agreement in place.
"I would certainly encourage every council in Scotland to join the register. It's an important way of finding a suitable match for children."
Deirdre Cilliers, joint head of social services for Stirling and Clackmannanshire councils, which use the register, said: "The Scottish Adoption Register has not been widely used by all local authorities due to concerns about the confidentiality of the information.
"I understand that one of the concerns has been about the requirement by some local authorities to have explicit agreements in place in terms of who the information referred to in the register belongs to.
"This issue is being addressed by the Scottish Government but has resulted in far fewer placements being made than had been expected.
"We are optimistic that more agencies will sign up, as this potentially would increase options for children in Scotland.
"Our view is that this is early days and if eight matches have been made so far then that is probably eight more than would have happened without the register."
In 2011, at least 12,000 children in Scotland were in care, while only about 300 were adopted.
Waiting times for children and approved adoptive families varied greatly, from a matter of months to five years.
The British Association for Adoption and Fostering (BAAF) was instructed by the SNP Government to set up the adoption register in March last year.
It is being run on a pilot basis for three years to establish whether or not it will be as successful as the adoption register for England and Wales, which has matched more than 1400 children and adoptive parents since its inception in 2004.
Sue Brunton, project leader for Scotland's register, said: "Adoption information from a number of different local authorities and charities is shared with the register and what we've had to do is ensure we have the necessary checks in place to be compliant with data protection.
"Penetration tests have been carried out – that's where you pay somebody to hack into the system to ensure that data is suitably protected.
"I do think the register is moving in the right direction. If I was sitting here at the end of next year with these figures, I might not be happy. I would like to have the majority of authorities referring to us by then."