An ab initio density functional theory study of the structure and stability of a select group of dopants in a diamond nanocrystal is presented. The dopants studied here are boron and nitrogen. These atoms have been included substitutionally in the center of a 29 atom nanodiamond crystal, and the entire structure relaxed using the Vienna Ab Initio Simulation Package. The relaxed structures are then described by the relaxation energy, the structural (total) energy and a qualitative examination of the overall change in structure and bonding, considered via examination of the electron charge density. It is anticipated that these results will provide a better understanding of the crystal stability of doped nanodiamonds for use in diamondoid nanodevices. (C) 2003 American Institute of Physics.