Nanocrystalline diamond (NCD) films were deposited on microscopic glass slides using the MW PECVD method (20 Torr, 710 °C, 0.8–1% CH4). After the growth period, the films were oxidized and subsequently hydrogenated, and some of them were doped with boron (NCD-B; 3,000–30,000 ppm B:C; leading to ρ ∼ 10–1 Ω cm for the highest doped films). The neutron depth profiling showed that in the near surface region (<800 nm) the boron (10B + 11B) content in the highest doped sample was about (1.9 ± 0.3) × 1021 B cm–3 (i.e., 1.1 ± 0.2 at% of B). The films were seeded with human osteoblast-like MG 63 cells (∼17,000 cells/cm2). On day 3 after seeding, the cell number on NCD (56,280 ± 1,090 cells/cm2) was significantly higher than that on NCD-B (by 27 ± 3%), glass slides (by 22 ± 3%) and polystyrene wells (by 36 ± 3%). On day 7, the cell numbers on both NCD and NCD-B films (351,170 ± 16,530 cells/cm2 and 310,020 ± 10,410 cells/cm2, respectively) became significantly higher than the values on glass slides and polystyrene dishes (218,800 ± 12,340 cells/cm2 and 223,400 ± 9,290 cells/cm2, respectively). Immunofluorescence staining showed that the cells on both NCD films assembled fine streak- or dot-like focal adhesion plaques containing alphav integrins or talin, and a mesh-like beta-actin cytoskeleton. The cells on NCD-B were brightly stained for osteocalcin, an important marker of osteogenic differentiation. Thus, both tested nanocrystalline diamond films gave good support for the adhesion, growth and maturation of bone-derived cells. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)