Dimethyl-ether has been identified in the interstellar gas in cold molecular clouds. It is therefore most probable that it can be trapped in the mantles of low temperature interstellar grains. Laboratory studies have been performed in order to simulate the photo-dissociation of dimethyl-ether trapped in ice at 10 K using vacuum ultraviolet radiation. Primary photo-products have been identified as formaldehyde and methane. They are both produced through two channels without subsequent reactions with water ice. We discuss the infrared spectroscopic measurements of dimethyl-ether and the mechanisms involved in the photo-dissociation of this organic molecule. (C) 2004 Elsevier B.V. All rights reserved.