Multi-scale solid particle aggregates designate aggregates of clusters, which are composed of smaller clusters, themselves composed by aggregated solid particles. There are usually 3 or 4 relevant scale levels of agglomeration. The final aim of this study is to define the relationships between the geometrical and optical characteristics of different aggregates. Indeed, a previous work of Gruy and Jacquier in 2008 [1] and [2] showed the existence of a narrow link between these two aggregate characterizations. The first step consists in modeling multi-scale aggregates with specific geometrical shape and optical properties. Thereafter, the aggregate characterization is performed. Following the Xu theory called GMM (Generalized Multiparticle Mie solution) exposed in his paper [3], the studied optical parameter is the scattering cross section, denoted, Csca in (µm²). In addition, the optical analysis is focused on aggregates with a high optical index. Concerning the geometrical characterization, several parameters are studied: the compactness, the number of the primary particles and the volume of the aggregates, successively. Using different 2D joint (geometrical/optical) representations, the correlation between the Csca values and the geometry of the aggregate is analyzed.