This research examines the metallorganic chemical vapor deposition process using tetrakis(3-methyl-3-pentoxy)cerium, Ce[OC(C2H5)(2)CH3](4), as a source material to prepare CeO2 films by two different mass spectrometric techniques: ionization by Li+ ion attachment and electron impact. The reaction by-products of (C2H5)(2)C = CH2 and H2O, respectively resulting from the pyrolysis of the source material and the dehydration reaction at the sticking of the precursor on the substrate surface, were detected as a result of the simple reaction integrated as Ce[OC(C2H5)(2)CH3](4)-> CeO2+2H(2)O+4(C2H5)(2)C = CH2 . The deposition was controlled by two mechanisms: desorption of the adsorbate from the surface site with the activation energy (E-a)=0.85 eV and decomposition of the source material with that of E-a=0.29 eV.