The semiconducting behavior of Nd-containing diamond layers, obtained from the gas phase by using a synthesis methodology, has been investigated in the range 100–500 K by performing Hall-effect and conductivity measurements. The diamond-based polycrystalline layers are characterized at the same time by relatively low values of hole density and by rather high values of conductivity, whereas the hole Hall-mobility values remain those typical of diamond single crystal. The results obtained in the range 100–500 K from the analysis of a representative sample are as follows: 2.4×1017–2.8×1018 cm−3 for hole density, 2.0×102–2.8×102 Ω−1 cm−1 for conductivity, and 6.5×102–6.4×103 cm2 V−1 s−1 for Hall mobility. Structural investigations performed by reflection high-energy electron diffraction confirmed that the incorporation of Nd doping atoms did not modify the diamond lattice parameters and did not lower the crystalline quality of the diamond film. © 1999 American Institute of Physics.