The article compares the determination of an SPE (Screen Printed Electrodes) electrochemical active surface (AS) by the analysis of cyclic voltammogram in ferro-ferricyanide using Koutecky equation and by confocal and electron microscopy. SPE reliability is influenced by mass transport of analyte to active electrode surface while the physical properties of SPE are reproducible and stable. The electrode reaction involves the upper layer of SPE. The AS is the same as the geometrical area. Other methods set the active/geometrical area relation to 2,03 +/- 0,04 (gold working electrode) and 4,35 +/- 0,08 (platinum working electrode). It is demonstrated that nanostructures on working electrode surface can be efficient at high frequencies (> 10 kHz). The active area of SPE determined by scanning electron microscopy or optical measurement exhibits a standard deviation lower than 2%. It proves SPE be reliable and precise electrochemical device under optimal hydrodynamic conditions. (C) 2014 The Electrochemical Society. All rights reserved.