Behavior of misfit and threading dislocations in HgCdTe/CdTe and HgCdTe/CdZnTe heterojunctions has been investigated by the dislocation‐pit etching technique. It is confirmed that by lattice matching the linear pit density caused by misfit dislocations on (1̄10) cleaved plane was decreased to 500 cm−1, which is about 1% of that obtained using CdTe substrates. It has been found that the density of the threading dislocations is not decreased by lattice matching, and nearly coincides with the dislocation density of the substrate.