The behavior of polymer-supported ambident anions derived from indane-1,3-dione towards alkylation under various conditions has been studied. Particularly, factors that may affect the yields of isolated products and their compositions have been considered. Almost exclusively the di-C-alkylation product could be isolated after relatively long reaction time. This unusual tendency toward di-C-alkylation is extensively discussed on the basis of the effect of reduced reaction time on the composition of resulting products in addition to a comparative study of mono-C- versus di-C-alkylation in indane-1,3-dione with the acyclic analogous dibenzoylmethane.