Controlling S-nitrosothiol decomposition, with the consequent release of nitric oxide, is a topic of great research interest. The incorporation of nitrosomercaptopyridine (SNO+) into the cucurbituril cavity results in a large increase of its nitrosation equilibrium constant. This effect being a consequence of the preferential stabilization of organic cations by the formation of host:guest complexes with CB7 results in a drastic reduction of the SNO+ denitrosation rate constant. Moreover, SNO+ encapsulation also prevents its decomposition yielding disulfide and nitric oxide. The expulsion of SNO+ from the cucurbituril cavity through the application of a chemical stimulus (competitive binding) results in controlled nitric oxide release as was confirmed by using a NO selective electrode.