Nanoscale Si-C-N composite powders with mean particle size less than 100 nm were synthesized by the RF induction plasma. Reactions of methylated silanes (Si(CH3)4 or SiCl3CH3) and NH3 or between nonmethylated silanes (SiCl4 or SiH4), C2H4, and NH3 were studied. Both the chemical composition and the morphology of nanoscale Si-C-N composites can be controlled by precursors as well as processing. Crystalline phase is mainly β-SiC, but sometimes a change of the lattice constant suggests a nitrogen incorporation into the SiC lattice. Annealing of the composite powders results in nanostructured powders, containing β-SiC as well as α-Si3N4 and β-Si3N4. Additionally temperature fields of the RF induction plasma were determined theoretically as well as experimentally.