To understand the low recovery of ruthenium from ruthenium nitrosyl nitrate solution by electro-deposition technique, electro-reduction behaviour of ruthenium nitrosyl complex [Ru-II-NO+](3+) in nitric acid medium was investigated using the potentiostatic electrolysis techniques, cyclic voltammetry and chronopotentiometry at Pt and glassy carbon working electrodes. Reduction of [RuNO](3+) was found to be quasi-reversible, one electron transfer process at both the electrodes. The diffusion coefficient (D (0)) of [RuNO](3+) species estimated by these techniques was in the order of 10(-8) cm(2) s(-1) and the heterogeneous electron transfer rate constant (k (s)) for the reduction of [RuNO](3+) was estimated to be about 10(-5) cm s(-1) using Klingler and Kochi equation. The very low diffusion coefficient value and the low separation percentage of Ru from ruthenium nitrosyl nitrate solution by electro-deposition technique are attributed to the existence of Ru(II) in different stable complexes instead of bare Ru(II) ions, in nitric acid medium.