The first comparative study between two new heterocyclic boron derivatives, viz. a (6-bromopyridin-3-yl)boronic ester, C(11)H(15)BBrNO(2), and (6-bromopyridin-3-yl)boronic acid, C(5)H(5)BBrNO(2), shows a small but not significant difference in their C-B bond lengths, which cannot explain the experimentally observed difference in their stabilities. The crystal packing of the boronic ester consists principally of van der Waals interactions, while the boronic acid molecules interact in their crystal through hydrogen bonds.