The radical addition of triorganotin hydrides, R3SnH (R = n-butyl, phenyl, neophyltin),to four unsaturated diesters of (11R, 12R)-9,10-dihydro-9,10-ethaneanthracene-11,12-dimethanol leads to products of cyclohydrostannation with an average yield of around 80%. Whereas the addition of these hydrides to diacrylate and dimethacrylate leads to the expected mixtures containing two and four distereoisomeric cyclized products respectively, the addition to di-2-methyl- and di-2-phenylcinnamate yields only four out of the sixteen possible stereoisomers. The observed high stereoselectivity is consistent with a radical tandem cyclohydrostannation mechanism. Full proton (H-1), carbon 13 (C-13) and tin 119 (Sn-119) nuclear magnetic resonance (NMR) data are given.