Nanosized zinc ferrite spinel powders of various compositions were produced in a radiofrequency (RF) thermal plasma from oxide mixtures and from co-precipitated hydroxides. Bulk and surface chemical compositions of the products were measured by ICP-AES and XPS. Phase conditions were determined by XRD. Morphology was investigated by SEM and TEM. In spite of the short residence time of reagents in the plasma reactor, a high degree of spinel formation was achieved. The Zn enrichment on the surface determined by quantitative XPS is attributed to a thin ZnO layer on the surface of the zinc ferrite particles. In zinc ferrous ferrites. an inhomogeneous distribution of Zn inside the grains may also exist.