Resumen: The analysis of Books 1-3 and 5-9 of the Collectio decem partium (10P) shows the astonishing parallel with the Panormia (only nineteen canons from the Panormia have not been included in 10P), although it seems to be a more systematic work than the Panormia. In this paper we intend to know the real characteristics and personality of the Collectio decem partium. To this aim, a detailed study of the material added to the Panormia (that is, mainly those in parts 4 and 10) is required. Parts 4 and 10 show an original and complex structure in which we find hardly any extensive blocks of successive canons belonging to the same formal source, but the compiler used many collections and rearranged the material under the headings of 10P. Currently there is no known collection that could have served as a model for the composition of parts 4 and 10, but it is likely that the appendices to the manuscripts PoPpTdVo of the Panormia constitute a testimony of a preparatory collection for 10P made of non-Panormia texts.