Electronic spectra of the S-1 <- S-0 transition of dimers of protonated benzaldehyde (BZH(+)) with Ar and N-2 are recorded by resonance-enhanced photodissociation in a tandem mass spectrometer. The S origins observed are shifted to higher frequency upon complexation with Ar (Delta S-1 = 300 cm(-1)) and N-2 (Delta S-1 = 628 cm(-1)). Ab initio calculations at the CC2/aug-cc-pVDZ level suggest an assignment to H-bonded dimers of L = Ar and N2 binding to the cis isomer of O-protonated BZH(+), yielding values of Delta S-1 = 242 and 588 cm(-1) cis-BZH(+)-L(H). Electronic pi pi* excitation results in a substantial increase of the proton affinity of BZH(+), which in turn destabilizes the intermolecular H-bonds to the inert ligands by 35%. The drastic effects of electronic pi pi* excitation on the geometric and electronic structure as well as the strength and anisotropy of the intermolecular potential (H-bonding and pi-bonding) are investigated.