We have obtained a variety of highly conducting cation radical salts of BEDT-TSeF(BETS)(bis-(ethylenedithio)tetraselenafulvalene) and asymmetrical pi-donors having a half of BETS skeleton, BEDT-STF(bis-(ethylenedithio)diselenadithiafulvalene), EDST((ethylenedithio)diselenadithiafulvalene) and EOST(4,5-ethylenedithio-4', 5'-(2-oxatrimethylenedithio)diselenadithiafulvalene). Crystal structure analysis of cation radical salts of BETS has revealed that BETS molecule has strong tendency to form 2-dimensional molecular arrangement. The crystal structures and electrical conductivities of radical salts of BEDT-STF, EDST and EOST were examined.