The topography evolution of a poly(o-toiuidine) layer (the object) electrodeposited on a polyfaceted Au single crystal from 0.5 M H2SO4 + 0.65 M o-toluidine aqueous solution at 25 degrees C has been studied combining nanometer scale ex-situ scanning tunneling microscopy and electrochemical techniques. A thin polymer layer structure consists of nodular elements following the substrate topography, whereas a thick polymer structure corresponds to a rather disordered structure made up of agglomerates formed by nodular elements with average diameter size d(s) congruent to 15 nm. In contrast to the former one, this structure is independent of the substrate topography. For thick layers xi, the root-mean-square roughness of the polymer coating, and L(s), the scan length, fulfill a xi proportional to L(alpha) relationship with alpha = 0.33 +/- 0.05 for L(s) > d(s) and alpha = 0.85 +/- 0.05 for L(s) < d(s). Accordingly, the polymer layer surface behaves as a self-affine fractal. For L(s) > d(s) the value of alpha agrees with that predicted for moving interfaces generated by the Eden model, whereas for L(s) < d(s) the value of alpha approaches that expected from an Euclidean surface. The topographic analysis of these polymer layers can be related to the kinetics of electrochemical reactions at polymer-coated Au electrodes.