Ru Schottky barrier diodes (SBD's) were fabricated on the Zn face of n-type ZnO. These diodes were irradiated with 1.8 MeV at fluences ranging from 1 ´ 1013 cm-2 to 2.4 ´ 1014 cm-2. Capacitance and current (I) deep level transient spectroscopy (DLTS) was used to characterise the irradiation induced defects. Capacitance DLTS showed that proton irradiation introduced a level, Ep1, at 0.52 eV below the conduction band at an introduction rate of 13±1 cm-1. A defect with a very similar DLTS signature was also present in low concentrations in unirradiated ZnO. I-DLTS revealed that this proton irradiation introduced a defect with an energy level at (0.036± 0.004) eV below the conduction band. This defect is clearly distinguishable from a defect with a level at (0.033± 0.004) eV below the conduction band that was present in the unirradiated sample. It is speculated that these shallow level defects are related to zinc interstitials or complexes involving them.