The known structural classifications of borates are based on the analysis of boron-oxygen radicals consisting of B-triangles and B-tetrahedra sharing O atoms to form more complicated structures. Such classifications ignore the possible presence and the role of hydrogen bonds, which may be the only bonds or additional bonds linking the [BO₃]-and [BO₄]-groups. A new detailed classification of hydrated boron compounds taking into account hydrogen bonds between the B-polyhedra is proposed.