An experimental study on the asymmetry of the Balmer Hβprofile in plasmas produced by microwaves at atmospheric pressure is presented. The study is based on the definition of several functions and parameters that quantify the asymmetry and different shape aspects of the profile. The study shows the experimental dependence of these characteristics on the electron density and control parameters such as the gas flow and the hydrogen admixture ratio. The possible use of these newly introduced profile characteristics to plasma diagnosis is discussed.