Molybdenum diselenide (MoSe2) was obtained by reacting stoichiometric quantities (1:2) of molybdenum hexacarbonyl [Mo(CO)(6)] and selenium in xylene under refluxing conditions. The obtained powder was identified as being a single phase of MoSe2 nanocrystallites by selected area electron diffraction, transmission electron microscopy, and energy dispersive X-ray analysis. The crystallite size varied between 10 and 35 nm.