The purpose with the present study has been to theoretically investigate the effect of P (or S) doping on the chemical vapor deposition (CVD) growth rate of diamond. Density functional theory (DFT) calculations under periodic boundary conditions were then used for the investigation of the highly symmetric H-terminated diamond (111) surface. It was shown that both the thermodynamics and kinetics of P (or S) substitutional doping during diamond (111) growth were severely affected by the dopants (as compared with the non-doped situation).As a result of the thermodynamic calculations, except for P doping in C layer 1, the thermodynamic driving force for the diamond (111) growth was found to be largely improved by positioning P within the upper surface region of the H-terminated diamond (111) surface, while the opposite was true for S-doping. The P doping had a local vertical influence on the H abstraction energies, which was not the situation for the S doping. Also, both P and S doping showed a local lateral influence on the H abstraction energies, which was more pronounced for P doping.As a result of the kinetic calculations, the vertical and lateral P doping showed no local effect on the H abstraction energy barriers. In fact, these energy barriers became zero for P positioned in C layer 2 and downwards and were also zero for longer distances from the H adsorbate. On the other hand, the vertical S doping showed a local effect on the calculated barrier energies, but no lateral effect. The calculated energy barriers were zero for all surface H adsorbates on the H-terminated diamond (111) surface when S was positioned in the 4th atomic C layer. The different results for P doping versus S doping could be explained by the fact that S contains one electron extra and that P has a larger electronegativity value.Consequently, the results showed that P positioned in the upper diamond (111) surface lattice caused an enhancement in the diamond growth rate. The exception was the position in C atomic layer 1, for which both P doping and S doping had no effect on the diamond growth rate. On the other hand, a growth rate improvement was only found for S positioned in the 4th C layer. Due to the much higher (i.e., more positive) theoretical incorporation energies of S dopants versus P dopants in the diamond lattice, it has here been concluded that P doping is more effective than S doping in increasing the growth rate of the H-terminated diamond (111). Especially when considering that the H adsorbates are very mobile on this diamond surface, which has been shown by ab initio MD simulations at experimental CVD temperatures. These observations correlate well with experimental results.