Data/MC Comparison for ECAL and HCAL

CMS has tuned its simulation program and chosen a specific physics model of Geant4 by comparing the simulation results with dedicated test beam experiments. CMS continues to validate the physics models inside Geant4 using the test beam data as well as collision data. Several physics lists (collection of physics models) inside the most recent version of Geant4 provide good agreement of the energy response, resolution of pions and protons. The validation results from these studies will be presented. Shower shapes of electrons and photons evaluate the goodness of the description of electromagnetic physics in Geant4 while response of isolated charged particles are used to examine the predictions of hadronic models within Geant4. Use of Geant4 to explain rare anomalous hits in the calorimeter will also be discussed.