Electronic and structural properties of two polymorphic modifications of 5-hydroxy-7-methoxyflavanone (pinostrobin) were theoretically investigated and compared with experimental crystallographic data. In the literature, four polymorphic modifications of pinostrobin had been reported. The present study has established that only two of them are relevant as they differ only in the position of the methoxy group whereas other structures are derived from the rotation of the phenyl group. Both structures differ in about 1.5 kJ/mol, but the activation energy of methoxy torsion was greater than 16 kJ/mol. In addition, both have similar electronic structures but it was established with slight differences in reactivity.