ABSTRACT: The hydraulic properties of the aquifer are necessary to be known for the regional assessment of natural resources and sustainable groundwater yield. The fact that specific capacity is correlated with hydraulic properties of the aquifer can simplify this parameter estimation. In the first part of the paper, a review of methodology used in Slovakia is given, together with practical examples. It is focused on a new contribution of using the conversion difference d value for selection of the representative section on the semi-log drawdown/time dependency plot for transmissivity coefficient estimation. The practical use is also showed. The next section describes the methodical procedures for regional assessment of the volcanic rock hydraulic parameters used in the world. Finally, the advantages and limitations of the described methodologies are discussed and the methodology appropriate for regional assessment of the hydraulic parameters in volcanic rocks of Slovakia is proposed.