In this work the authors study field-emission properties of a class of emitters formed by coating the multi-walled nanotube (MWNT) polymer composite film onto the flat metal substrate. They have obtained emission currents up to 100 mA. In order to understand the physical and chemical processes in the working composite emitter, the authors have elaborated the experimental technique combining the mass spectrometry registration apparatus with the field-emission unit. (c) 2008 American Vacuum Society.