Nanosized manganese oxide particles have been synthesized via vapor phase growth. The diameter of the nanoparticles can be controlled by the growth temperature: the higher the temperature, the larger the diameter of the particle. Magnetization measurements show that the manganese oxide nanoparticles have an obvious ferromagnetic behaviour with the Curie temperature around 40 K. The latter is size-dependent, namely: the smaller is the diameter of the particles, the lower is the Curie temperature. (C) 2003 Elsevier B.V. All rights reserved.