Electrochemical behaviour of adsorbed NO molecules on Pt(100) electrode has been studied in perchloric acid solutions by means of cyclic voltammetry. According to literature data, saturated NO adlayer with coverage of ca. 0.5 ML is formed at open circuit conditions in nitrite solution as a result of disproportion reaction. The adlayer is stable in the range of 0.4-0.9 V, NO molecules are oxidized at 0.9-1.1 V and can be reduced to ammonia at potentials less than 0.4 V. Stability of the adlayer depends on surface coverage and extent of the ordering. Unsaturated NO adlayer demonstrates redox transformations NO↔NH 3 at 0.5-0.8 V.