This report describes the Na2PtCl4 catalyzed C-H arylation of arene substrates with diaryliodonium salts. The site selectivity of these reactions is predominantly controlled by steric factors. Remarkably, Na2PtCl4-catalyzed naphthalene arylation proceeds with opposite site selectivity compared to that obtained with Na2PtCl4 as the catalyst. Preliminary mechanistic studies provide evidence for a Pt-II/Pt-IV catalytic cycle involving rate-limiting C-C bond-forming reductive elimination.