Computed Tomography (CT) has become an important tool for diagnosing cancer and to obtain additional information on different clinical issues. The radiation dose values in computed tomography depend on the scan acquisition protocol. Today, it is a very fast, painless and noninvasive test that can be performed high quality images. Therefore, it is indispensable to improve protocols, seeking smaller doses, without impairing the diagnostic quality of the image. The doses received are related with risks of stochastic effects. Based on this information, in this study, a cylindrical phantom and an oblong phantom made of polymethylmethacrylate were used representing an adult chest, The oblong phantom was built based in the chest cut section, including axillary region, with the same cut area of the cylindrical phantom. A comparative study of chest phantoms was performed in a Toshiba scanner, Aquillion model with 80 channels. The phantom central slice has been irradiated successively, and measurements in five different points of each phantom have done using a pencil ionization chamber. From the measurements, we obtain values of weighted and volumetric Dose Index (CTDIw, CTDIvol). The scans have been performed with the routine chest acquisition protocols of the radio diagnostic service with the voltage of 120 kV and additionally with the voltage of 135 kV. This study has allowed comparing the distribution of absorbed dose in two phantoms using two different voltages.