Lattice dynamical calculations using a shell model are carried out for the geophysically important mineral zircon, ZrSiO4. The model parameters are adjusted so that the model satisfactorily reproduces the literature data on structure, elastic constants and optically active modes. Phonon dispersion relations are measured on a single crystal using coherent-inelastic neutron scattering on the PRISMA spectromter at the UK ISIS facility. The one-phonon structure factors are calculated to preselect the Bragg points for the measurements and to assign measured phonon signals to different branches. The phonon dispersion relations measured are in good agreement with the calculations.