More country communities should target international migrants as a "top priority" to help boost shrinking populations, a new study says.

"The Missing Migrants" study cites case studies where small regional communities that opened their arms to migrants turned their fortunes around.

A citizenship ceremony in Nhill in 2013.

"If more international migrants settled in regional Australia, our regional population would grow at the same pace or even faster than the capital cities," the report said.

"International migrants make their most important contribution in small rural towns that are most at risk of population decline."