Mean particle diameters may be used to describe and to model physical, chemical or physiological properties of products or materials containing dispersed phases. An empirical method was developed to select the proper type of mean diameter from experimental data, if this mean diameter is not known a priori from theoretical reasoning. The present method uses mean diameters, (D) over bar (p, q), defined according to the Moment-Ratio (M-R) definition system. They are expressed as the 1/(p-q)-th power of the ratio of the p-th and the q-th raw moment of the number density distribution of the particle sizes. After calculation of the mean diameters, (D) over bar (p, q), the relationships between the product property and these mean diameters are investigated statistically. The selection method has been illustrated by four examples, three of which stem from a high shear granulation experiment in the field of detergent processing. The fourth example is concerned with a visual ranking of bubble size distributions of chocolate mousse samples. The data set of each example consists of a set of particle size distributions and the corresponding physical product properties that are influenced by the particle sizes. Hypotheses are formulated to explain the types of selected mean diameters. Application of the selection method gives mean diameters, (D) over bar (p, q), a clear physical look and identity, replacing their anonymity. Sharing worldwide results of applications of the newly developed selection method, will lead to a build-up of knowledge of physical meanings and application areas for the types of the mean particle diameters. This will support decision-making in product development. The examples used to develop the selection method clearly demonstrate the physical relevance of the previously developed nomenclature system for mean particle diameters, (D) over bar (p, q).