The micro injection molding process is nowadays considered as a suitable technology for manufacturing microstructured surfaces. The molded part geometry influences the filling flow of the melt inside the mold cavity as well as the final quality of the replicated micro features. In this work, the replication of a micro-structured surface is studied in relation to the thickness of the molded part. The influence of this geometrical parameter is investigated using state-ofthe- art micro injection molding technologies. In particular the effects of a rapid heat cycle molding process, cavity air evacuation, part thickness and their interactions on the replication of a micro-structured surface are experimentally evaluated, considering the filling pattern of the polymer melt in the main cavity as well as in the micro features. The obtained results provide useful information for an effective approach to the design of both the part and the process, indicating that the selection of process parameters should be related to the design of the mold cavity.