The first observation of photosubstitution products in electrospray mass spectra is reported. The solvent-coordinated Ru(II) complex ions created by photodissociation of Ru(2,2’-bipyrazine)(3)Cl-2, Ru(2,2’-bipyridine)(3)X(2) (X = Cl- and ClO4-), and the related complexes in acetonitrile solution were directly detected by on-line electrospray mass spectrometry. The mass spectra were well explained in terms of coordinating ability of counterions and solvent. Collision-induced dissociation in the gas phase was an important process particularly for interpretation of photoproducts such as weakly-bound solvent-coordinated complexes. It was found that the electrospray technique, combined with a flowing photoreaction cell, can potentially be used to identify photoproducts or intermediates.