PbYb 1/2 Nb 1/2 O 3 and PbYb 1/2 Ta 1/2 O 3 single crystals were grown by the flux method. Crystals that were transparent, brown and in the form of an octahedron with well developed {111} faces and edge dimensions up to 6mm were obtained. From XPS analysis the following chemical formulas were found: Pb 1.10 Yb 0.35 Nb 0.57 O 2.98 (PYN) and Pb 0.84 Yb 0.83 Ta 0.60 O 2.72 (PYT). This shows that the PYN crystal has a composition that is closer to the nominal one in comparison with that of the PYT crystal. The magnetic results show that the amount of magnetic Yb 3+ is similar for both compounds. Both compounds are Van Vleck paramagnets as a result of the crystal field effect. The excess of ytterbium in PYT is as non-magnetic Yb 2+ situated probably in the lead position due to the ionic radius size and valency similarity. Such ytterbium division into two valencies ensures charge neutrality of the PYT crystal.