Infrared spectroscopy (IR) was used as the preferential method for determination of the composition of calculi and scanning electron microscopy (SEM) for observation of the IR shape. Our results show the role of SEM for visualisation of the internal ultrastructure and architecture of calculi in children. The authors confirm their previous hypothesis that phosphates favour the nucleation of other compounds, and demonstrate the presence of some trace elements which could play an important role in lithogenesis (eg Si).