The size of microdroplets of dodecane of approximately 5 pm diameter immobilised on a regular array of hydrophobic polymer blocks of a partially blocked electrode is determined by comparison of a simple electrochemical procedure with simulations. The electrochemical procedure is based on a simple Cottrellian-like potential-step experiment, where the current response is monitored as a function of time. Excellent agreement is found between theory and experiment thus giving physical support for the expected transition in diffusion layer shape and size. (c) 2006 Elsevier B.V. All rights reserved.