This work, carried out on the phase 2 of the OPUR (Observatory of Urban Pollutants) research programme, aims to study the spatial variability of the aliphatic (AH) and polycyclic aromatic hydrocarbon (PAH) loads within the Parisian combined sewer during dry and wet weather periods. For both periods, investigations reveal a quite homogeneity of the AH and PAH loads between the six urban catchments considered (from 42 to 2 581 ha). This observation mainly suggests that the hydrocarbon loads in dry and wet weather flows do not change in relation to the spatial scale. The second Part of this article focused more especially on the transfer of hydrocarbons during wet weather period. Therefore, contributions from wastewater runoff and in-sewer deposit erosion to the wet weather pollutant loads were assessed. Whatever the site considered the erosion of in-sewer deposits constitute an important source, contributing to 40 and 66% of the total AH and PAH loads, respectively. In the same way, runoff contribute mainly to the AH loads (50%) and to a lesser extent to the PAH loads (17%).