A comprehensive work was carried out to investigate natural radionuclides of U-238, Th-232 and K-40 in 73 soil samples collected from islands of Adir, Carpanak and Akdamar on the Van Lake (Turkey) located at Eastern Turkey. Radioactivity concentrations of these radionuclides were measured by using a gamma spectrometer with NaI(Tl) detector to be from 4.11 to 77.1 Bq/kg, from 6.0 to 70.0 Bq/kg and from 133.05 to 749.77 Bq/kg with the mean values of 33.33 Bq/kg, 36.68 Bq/kg and 478.19 Bq/kg, respectively. In addition, the absorbed gamma dose rate in air (D) and annual effective dose equivalent (AED) were found to be 57.5 nGy/h and 70.5 mu Sv/year, respectively. We have shown that our results might be related to the geological formation type. The results were compared with some published ones in Turkey and the World, which were found within acceptable limits.