The paper contains the results of experimental studies on water atomization process in effervescent nozzle in one-phase and two-phase systems. The gas phase flow rate causes the changes in characteristic parameters of atomization. The gas flow rate has certain effect on the Sauter Mean Diameter SMD values. SMD for airliquid systems investigated is decreasing with increase of gas volume rate. It is observed that SMD values are increasing with increase of liquid volume rate. The larger SMD values for one-phase flow in comparison with two-phase flow have also been observed. The increase of SMD value has been observed with a decrease of an outlet diameter of an effervescent nozzle.