Positrons, positive muons and deuterons were used - when applicable - to probe the production and thermal stability of defects induced at room temperature either by electron irradiation or He-ion implantation in zirconia stabilized by yttria in the cubic phase. No change in the positron lifetime or in the muon spin relaxation occurs after electron irradiation, indicating a positron saturation trapping in the annealed state, owing to the presence of structural defects inherent to phase stabilization. In contrast, after helium implantation, even at low fluence (similar to 10(14) cm(-2)), Slow positron implantation spectroscopy reveals the presence of a new type of defect (being more trapping effective than the native ones), whereas neither positronium nor muonium are detected. The diffusion of helium was followed after He-3-ion implantation and subsequent annealing using the He-3(d,p)(4) He nuclear reaction. A two-Gaussian distribution fit indicates that a part of the helium atoms is trapped at the projection range location, most likely in gas bubbles, while the other part diffuses and out-gasses after heat treatment already at around 1/5 of the melting temperature. In spite of differences in depths and concentrations probed by the present techniques, a fairly good correlation is observed between the various results. (c) 2007 Elsevier B.V. All rights reserved.