The findings by Paul Kench at Auckland University and Arthur Webb at the South Pacific Applied Geoscience Commission in Fiji seem to contradict earlier predictions that swelling seas influenced by global warming would inundate low-lying islands.
The researchers used archival aerial photos and satellite images to plot changes in the land surfaces of 27 islands.
Writing in the journal Global and Planetary Change, they said they found that only four of the islands have shrunk since the 1950s, while 43 percent of them remained stable and another 43 percent grew in size.
The atolls appear to be holding their own despite higher seas due to coral debris, land reclamation and sediment, the researchers say.
Other scientists warn that sea level rises will accelerate greatly over the coming decades, eventually overwhelming low-lying islands.