A regioselective radical C-H trifluoromethylation of aromatic compounds was developed using cyclodextrins (CDs) as additives. The C-H trifluoromethylation proceeded with high regioselectivity to afford the product in good yield, even on the gram scale. In the presence of CDs, some substrates underwent a single trifluoromethylation selectively, whereas mixtures of single- and double-trifluoromethylated products were formed in the absence of the CD. 1H NMR experiments indicated that the regioselectivity was controlled by the inclusion of a substrate inside the CD cavity.