The influence of eccentricity of the central tube delivering the liquid to be atomized on the performance of a coaxial prefilming air-assist atomizer has been studied experimentally. Local droplet size measurements performing using a phase Doppler anemometer show the dependence of the droplet diameter on the relative eccentricity of the liquid tube. This article presents the experimental technique and a dimensional analysis of the data. A comparison of experimental data with the developed empirical equations shows good agreement. The coefficients of the empirical equation lead to a quantification of the deviation of the Sauter mean diameter that is dependent on the leading parameters even in the spatial direction.