The complexes of cytidine (C) with Ag+ and adenosine (A), guanosine (G), inosine (In) and caffeine (Caf) were studied by electrospray ionization mass spectrometry (ESI-MS). Both collision-induced dissociation (CID) “in-source” and CID MS/MS experiments were performed. The stability of [C+G+Ag]+ and [C+In+Ag]+ ions in the gas phase was found to be much higher than that of [C+A+Ag]+ and [C+Caf+Ag]+ ions. It is reasonable to conclude that guanosine and inosine form bidentate complexes with the silver cation, by the N7 atom and O=C6 oxygen atom, whereas adenosine and caffeine form monodentate complexes, by the N3 atom of adenine and the N9 atom of caffeine.