Dithiophosphates are used in many different industrial applications. To explain their functions and properties in these applications, a fundamental understanding on a molecular level is needed. Potassium O,O'-Dibutyldithiophosphate and its anion have been investigated by means of a combination of DFT and P-31 CP/MAS NMR and infrared spectroscopy. Several low-energy conformations were studied by DFT. Three different conformations with significantly different torsion angles of the O-C bond relative to the O-P-O plane were selected for further studies of infrared frequencies and P-31 NMR chemical-shift tensors. A good agreement between theoretical and experimental results was obtained, especially when the IR spectra or P-31 chemical shift tensor parameters of all three conformations were added, indicating that, because of the low energy difference between the conformations, the molecules are rapidly fluctuating between them.