The aim of this work was to investigate the morphology, average size, and the electrochemical behavior of platinum nanoparticles electrodeposited from water and mixed water-ethylene glycol solutions of the electrolyte of H2PtCl6 and H2SO4 at a rotating disk electrode coated with Vulcan XC-72 carbon powder. Cyclic voltammetry and linear sweep voltammetry were used to determine the electrochemically active surface area (ESA) and oxygen reduction reaction (ORR) activity of the prepared Pt/C materials, respectively. XRD and scanning electron microscopy were used to study the influence of the electrodeposition methods applied on the morphology of platinum particles deposited in water and mixed water-ethylene glycol solutions. The average size of Pt crystallites was in the range of ca. 6-10 nm, and the average size of deposited Pt particles was in the range of ca. 30-150 nm. It was found that the presence of ethylene glycol in the electrolyte solution increased the overpotential of electrodeposition and it also strongly affected the morphology of Pt deposits when constant current electrodeposition was employed. Moreover, it was shown that pulse current electrodeposition is a more effective method compared to constant current electrodeposition method for the preparation of the Pt/Vulcan electrode with high ESA of Pt and enhanced catalytic activity toward ORR. The results obtained concerning the morphology and the spatial distribution of platinum particles electrodeposited on the surface of carbon support at different conditions demonstrate new possibilities to improve synthesis of Pt/C by electrodeposition methods.