The study of radiation fields around the cyclotron roomwas carried out for the Proton-Therapy-Center in Prague (Czech Republic).The 230 MeV proton cyclotron will be installed there as well asadditional components located along the beampath. The ambient doseswere computed by taking into account 3 major sources of secondaryradiation (neutron and photon) – the cyclotron, energy degraderand its collimator. The fluxes of neutrons/photons produced by protonswere computed using Monte Carlo code MCNPXTM 2.5.0. Energyand angular distributions were computed for various targets and protonbeam energies. Different physical models of high-energy proton interactionswere studied as well. The annual charge at the cyclotron exit wasbased on the “patient model” (distribution of treatment type) establishedfor a similar therapy center in Essen (Germany). Calculated datawere used as an approximation of the radiation field of the most significantsources of radiation (graphite degrader, tantalum collimator). Fluence-to-doseconversion factors from ICRP-74 were used for the annual dose equivalentevaluation. With these results, the shielding analysis in the Therapy-Centerwas performed in the context of the current legislation requirements.