The reactions of chromium and chromium fluoride monocations CrFn+ (n = 0-4) with phosphane are investigated by Fourier-transform ion cyclotron resonance mass spectrometry. Besides condensing slowly with phosphane, Cr+ is unreactive. The ionic products of the chromium fluoride cations are as follows: (i) CrF+ yields CrPH2+ and subsequently CrPH3+; (ii) from CrF2+, the ions PH3+, Cr+, and CrF2H+ are generated; and (iii) both CrF3+ and CrF4+ yield PH3+. The structure and formation of [Cr,P,H-3](+) are investigated by collision-induced dissociation and isotopic labeling experiments. For the neutral species [P,H-3,F-2] formed by reaction of CrF2+ with phosphane, the structures are interrogated by quantum-mechanical calculations at the MP2/6-31++G** level of theory.