Diamond is a very attractive material for use as a radiation detector due to its inertness, radiation hardness and tissue equivalence. The development of diamond radiation detectors was limited by the availability of good and reproducible natural samples. The advent of chemical vapour deposition techniques has allowed these drawbacks to be overcome and applications of CVD diamond in x-ray and nuclear dosimetry was explored by several researchers. In this paper we report the fabrication and characterisation of miniaturised (0.1 mm³) x-ray detectors made from polycrystalline diamond films (10/20 µm thick) deposited by hot filament vapour deposition technique on metallic (tungsten) 300 µm diameter tips. The detector response to x-ray flux produced by an x-ray generator with peak energies ranging from 50 to 250 keV and by electron linear accelerator used in radiotherapy with a peak energy of 6 MeV has been investigated. The linearity and the sensitivity of the detector as a function of dose rate at different photon energies has been evaluated and the collection length has been estimated by analysing the behaviour of the photocurrent as a function of the applied bias voltage.