© 2021, Saudi Society for Geosciences.Rock mass elasticity modulus, rock mass deformation modulus, static elasticity modulus, and dynamic elasticity modulus are the geotechnical properties of a rock mass and intact rock. However, these moduli are confused with each other in the literature. These moduli are determined using different test techniques. These values are different values and should not be used interchangeably. The main purpose of this paper is to illustrate the differences and build a statistical relationship between these rock moduli. The moduli determined in Deriner/Artvin and Ermenek/Karaman dam investigation studies were used and compared in this study. The rock mass elasticity modulus (ED) from the dilatometer test, rock mass deformation modulus (DD) from the dilatometer test, rock mass elasticity modulus (EH) from the plate-loading test, rock mass deformation modulus (DH) from the plate-loading test, intact rock static elasticity modulus (ELS) from laboratory tests, and intact rock dynamic elasticity modulus (ELD) from laboratory tests were correlated with regression analysis. Empirical equations obtained by the regression analysis performed between rock moduli revealed high correlation coefficients. The ratio of the modulus of deformation and modulus of elasticity determined from in situ test at the Deriner dam site was close to 1 at smaller modulus values but the ratio value was scattered at higher modulus values. The ratio of the laboratory determined dynamic elasticity modulus and static elasticity modulus approached 1 by decreasing weathering. Differences between moduli are demonstrated in this paper. The empirical equations proposed in this study were developed with a limited amount of data and every rock mass and intact rock sample have specific modulus values. The equations determined in this study should not be used for other projects or a cross check should be performed.