The current status of modeling on CVD processes to produce thin films is summarized in this review. The experimental methodologies for extracting the essential chemistry in CVD reactors had been developed to efficiently design CVD reactors. Tubular wall deposition method provides information on the rate limiting step of the deposition process and the rate constants. Molecular size of film forming species can be estimated from the deposition rate profile in the tubular reactor if the process is limited by the gas phase diffusion. Microcavity-deposition method provides the tool to analyze the surface reactions. The microcavity-deposition method can be combined with macrocavity-deposition method to extract the important reaction pathways like as the intermediate deposition. The use of computer chemistry is also useful in detecting key reactions and it may be used to construct new deposition chemistry. The computer fluid dynamics coupled with the chemistries obtained from these approaches will be a powerful tool to design CVD reactors.