The difluorinated ring in 2,4-difluorobenzaldehyde isonicotinoylhydrazone, C13H9F2N3O, (I), is disordered over two sets of sites with unequal occupancy. The molecules of (I) are linked by a combination of N-H...O and C-H...O hydrogen bonds into chains of rings, which are linked into sheets by a single pi-pi stacking interaction. In 2,3-dichlorobenzaldehyde isonicotinoylhydrazone, C13H9Cl2N3O, (II), the molecules are linked by a combination of N-H...N, C-H...N and C-H...O hydrogen bonds into sheets of R(4)(4)(14) and R(4)(4)(26) rings.