Spin-unrestricted CNDO/2 calculations for the radicals (OH)₂(O)P-CH₂, (CH₃)₃P⁺-CH₂ and (CH₂CH)₃P⁺-CH₂ are reported. In each case potential energy profiles for the rotation of the CH₂ group around the P-C bond are calculated with optimization of the P-C distance. The results show (i) that it is essential to introduce d-orbital participation on phosphorus, (ii) that the height of the barrier to internal rotation depends critically on the symmetry of phosphorus environment, and (iii) that the delocalization of the unpaired electron to the phosphorus nucleus is very small.