The accuracy of the PRRT dosimetric procedure depends on the dosimetrist's personal skills in the step of determining the accumulated activity in the relevant organ. The detection of activity involvement is done manually by the dosimetrist using a mouse on SPECT images. Creating custom ROIs may create differences in dosimetric calculations. The purpose of this study is to investigate the effect of Dosimetrist performans on critical organ dose calculations in PRRT. To assess the biodistribution of the radiopharmaceutical and calculate organ-specific activity, serial SPECT/CT imaging was performed at 4, 24, 48, and 96 hours post-administration. Bu using SPECT images, VOIs counts were separately determined by using ROIs on the relevant organ created by 3 independent Dosimetrist. Statistical tests were applied to the counts to determine whether there was a significant difference between the counts detected by the 3 independent dosimetrists. The ANOVA test is an analysis of variance method used to determine whether there is a statistically significant difference between the means of three or more groups. In the Anova test, if p < 0.05, there is a statistically significant difference between the groups. If p ≥ 0.05, there is no significant difference between the groups, the observed differences may be due to chance criteria were taken into account. We conducted a statistical evaluation (ANOVA Test) between the counts determined by three different dosimetrists, and no significant difference was observed between their results.