Cobalt thin films are deposited by metal-organic (MO)CVD, under various experimental conditions, on Si and SiO2 substrates. The precursors used are cobalt nitrosyl tricarbonyl, Co(CO)3NO, cobalt acetylacetonate, Co(acac)2, and cobalt carbonyl, Co2(CO)8. Emphasis is given to the delivery method of each precursor, especially to a new technique of aerosol delivery. The films are thoroughly examined in terms of microstructure and surface morphology in order to establish relevance to magnetic properties. It is found that Co films deposited from Co2(CO)8 dissolved in dichloromethane are characterized by a high degree of planarity and purity, while exhibiting a non-hysteretic giant magnetoresistance (GMR) behavior in the presence of an externally applied magnetic field normal to their surface.