High dose implantation of hydrogen into silicon and subsequent annealing induce a splitting of silicon. The state of hydrogen and the implantation induced defects are of scientific and technological interest. Samples implanted with 1 (.) 10(16) and 5 (.) 10(16) H+/cm(2) at an energy of 60 keV were investigated after different thermal annealing treatments with the pulsed positron beam as a function of the positron energy and the specimen temperature (80K to 500K). There is clear evidence of growth of defect clusters with increasing annealing temperature which correspond in depth with the mean projected range of the implanted hydrogen atoms. In addition to the large defect agglomerates, there are most likely shallow positron traps which are effective only when the specimens are measured at low temperature.