Permeability, the most important reservoir property of rock can be directly measured on samples and determined using various statistical relationships between petrophysical parameters. We tested usefulness of Swanson parameter obtained from the mercury porosimetry results and T2 relaxation time from the Nuclear Magnetic Resonance (NMR) to find adequate formulas to improve permeability determination. We used the Devonian carbonates and the Carboniferous mudstones from the Western Carpathians and the Rotliegend sandstones from the Foresudetic Monocline in Poland. New factors as Swanson parameter or T2 relaxation time in NMR are effective in creating empirical relations describing reservoir parameters of rocks. Precision of measurements and features of rock decide about quality of the relations and their effectiveness.