An efficient synthesis of selenothiophosphinic acid salts is achieved by reacting selenothiophosphinic acid S-(2-trimethylsilyl)ethyl esters with ammonium or alkali metal fluorides. The Xray structure analysis of the potassium 18-crown-6 selenothiophosphinic acid salt shows that the salt is monomeric. Alkylation of the salts proceeds at the selenium atom whereas acylation occurs at the sulfur atom.