Coincidence Doppler broadening (CDB) and lifetime measurements for silicon implanted with helium ions (60 keV, 1 x 10(15) /cm(2)) have been performed. In the as-implanted sample, divacancies; are induced in the near-surface region, while they arc passivated by He near the mean projected range. After annealing at 300degreesC, the lifetime of the positrons trapped in the defects is 280 ps and the peak due to He atoms in CDB ratio curve is enhanced. The diffusion of He and clustering of vacancies take place and V(x)He(y) (x-y=1) complexes are formed throughout the implanted region. Anneal at 500degreesC leads to release of He from the sample and, as a result, V(x)He(y) complexes are transformed into V(4).