The neighboring group effect of five- and six-membered heteroaromatic rings toward a remote cationic center was studied by the electrophilic addition reactions of norbornadiene fused with heteroaromatic rings. The neighboring heteroaromatic rings were also found to effect the π-facial selectivity in the electrophilic ene and addition reactions of fused isopro-pylidenenorbornenes. This account traces the ideas and discoveries in the studies on the neighboring group effect of heteroaromatic rings, and the results of ongoing studies from our group are overviewed.