Nano-sized platinum metal particles have been incorpQrated in mesoporous AIMCM-41 by y-radiolysis of the sample exchanged with [Pt(NH₃)₄]²⁺ ions. The sample has been characterized by a variety of techniques such as low angle X-ray diffraction, MAS NMR spectroscopy and transmission electron microscopy to establish the formation of both AlMCM-4l and nano-sized Pt metal particles. TEM shows a broad distribution in the size of Pt particles in the range of 10-20 nm. The catalytic activity of Pt/AlMCM-4l sample has been tested by room temperature hydrogenation of cyclohexene to form cyclohexane and temperature programmed hydrogen desorplion studies.