Groundwater has a direct impact on the excavation operations and support systems of underground mining activities. Therefore, it is necessary to investigate the rock mass permeability. Lugeon test is one of the in-situ tests being used for measurement of the rock mass permeability. Discontinuity orientation, spacing, aperture, surface quality, the presence and type of filling play important role in the permeability of the rock mass. Commonly used parameters, RQD (Rock Quality Designation) and Dc (Discontinuity Condition Rating of the RMR) were selected for prediction of the rock mass permeability. Additionally, the field stress directly influencing the interlocking of the discontinuities is taken into account in terms of depth and included in the predictions. Foreseeing that the rock mass permeability has a complex mechanism, multiple regression methods were employed in order to relate rock mass parameters with Lugeon value. Although the presented equations can be used in similar field conditions, it must be recalled that the in-situ testing remains to establish a basis for the investigations.