Since thermalized positrons in materials are sensitively trapped at their affinitive sites, elemental analysis using coincidence Doppler broadening of positron annihilation gives us the elemental information on the sites exclusively. Here we report, as a good example, the analysis of positron affinitive embedded clusters: ultrafine Cu clusters in Fe. The positron annihilation results are compared with those obtained with a three-dimensional atom probe field ion microscope. Theoretical calculations of positron annihilation are also used to discuss these experimental results.