One in 10 young people aged between 16 to 24 are leaving the Highlands, a breakdown of census figures suggests.
More than 12% of young people leave the Western Isles
One Highland MSP is calling for an urgent review of economic and crofting policy to ensure they either stay or return to the area.
Almost 4,000 youths left the Highlands and Islands in 2000 and were living elsewhere in 2001.
The Western Isles lost the greatest proportion, 12.4%, while Inverness, Nairn and Lochaber lost 11.3%.
Highlands and Islands Enterprise has warned this could have a severe effect on the economy, although economic migrants could be part of the solution.
Highland MSP Rob Gibson wants further research into the number of graduates who do not return and the proportion of people coming into the area who are retirees and short-term economic migrants.
The SNP MSP has called for a policy review to improve job opportunities and the cost of living.
He said the crofting system should be used to provide housing to prevent a "brain drain the area could ill afford".