In this communication, we report the results of the investigations carried out on the stability of discontinuous Cu films deposited on polymethylmethacrylate coated substrate heated to a temperature above the glass transition temperature of the polymer. It was reported that evaporated materials on such substrates form a subsurface particulate structure. It was found that in Cu films post-deposition instability persisted on a softenable substrate similar to the behavior of Cu on glass. On exposure to atmosphere, the resistance increased due to the interaction of atmospheric gases and water vapor. A film deposited at room temperature and and heated also behaved in a similar fashion when exposed to atmosphere.