A study was performed using multi-phase flows of water and mineral oil in a pressure-swirl atomizer with a multi-hole oil injector to produce O/W emulsions. The volumetric fraction of the oil dispersed phase in the emulsions ranged from 0.1 to 0.3, and the volumetric flow rates of the emulsions were between 1.38.10(-5) and 5.55.10(-5) m(3)/s. The structures of the resulting emulsions were determined. It was found that as the oil concentration increases, the histograms of oil droplet diameters become wider and are shifted towards larger diameters. The mean volume-surface diameter of droplets, for which a correlation equation is proposed, increases as the volume concentration of oil increases and as the volumetric flow rate of the emulsion decreases. The proposed solution is an alternative to the process of producing emulsions in mechanical mixers, particularly if it is possible in the existing process installation to achieve an adequate character of two phases flow. (C) 2017 Elsevier B.V. All rights reserved.