The influence of 70 keV He+ ion implantation and subsequent annealing of Cz-indium phosphide (InP) samples has been investigated using a slow positron beam-based Doppler broadening spectrometer. Three samples with ion fluences of 1 X 10(16), 5 x 10(16) and 1 x 10(17) cm(-2) were studied in the as-implanted condition as well as after annealing at 640 degrees C for times between 5 and 40 min. It was found that the line-shape parameter of the positron-electron annihilation peak in the implanted layer increases after 5 min annealing, then after longer annealing times it starts to decline gradually until it reaches a value close to the value of the as-grown sample. This implies that vacancy-like defects can be created in InP by He implantation followed by shortthermal annealing at T > 600 degrees C. Comparison of the results with a study where cavities were observed in He-implanted InP has been carried out. (c) 2005 Elsevier B.V. All rights reserved.