Supercritical antisolvent (SAS) technique is an appropriate process to obtain micro- and nanoparticles. The application of this process has, until now, been explored in a variety of different fields including: explosives, polymers, pharmaceutical compounds, colouring matter, superconductors, catalysts, and inorganic compounds. Biocompatible and biodegradable polymers are playing more and more important roles in pharmaceutical areas such as tissue engineering and drug delivery. Formulation of these polymers into suitable solid-state forms plays an important role in safety, stability, and efficiency of the products. Ethyl cellulose is commonly used as drug carrier in controlled delivery systems. In this work, particles of ethyl cellulose have been precipitated by SAS using CO2 as antisolvent and dichloromethane (DCM) as solvent. We studied the effects of concentration on the particle size distribution (PSD) of the precipitates. Ethyl cellulose size-controlled particles have been produced in the micrometer range 3.8-5.0 mu m, and an increase of the mean particle diameter (MPD) was observed with the increase of the concentration of the solution.