The nature of resonance-assisted hydrogen bonds (RAHB) is still subject of an ongoing debate. We therefore analyzed the sigma and pi charge redistributions associated with the formation of intramolecular hydrogen bonds in malonaldehyde (MA) and its saturated analogue 3-hydroxypropanal (3-OH) and addressed the question whether there is a resonance assistance phenomenon in the sense of a synergistic interplay between the sigma and pi electron systems. Our quantum chemical calculations at the BP86/TZ2P level of theory show that the pi charge flow is indeed in line with the Lewis structure as proposed by the RAHB model. This typical rearrangement of charge is only present in the unsaturated system, and not in its saturated analogue. Resonance in the pi electron system assists the intramolecular hydrogen bond by reducing the hydrogen bond distance, and by providing an additional stabilizing component to the net bonding energy. The sigma orbital interaction plays an important role in the enhanced hydrogen bond strength in MA as well. However, there is no resonance assistance in the sense of an interplay between sigma charge transfer and pi polarization; sigma and pi contribute independently from each other.