Precipitated Calcium Carbonates (PCC) acts as rheology modifier in adhesives and sealant formulations as well as filler in polyolefines to introduce paintability, stiffening and toughening. In the presented project the combination of PCC with cellulose fibers for increased modulus and strength was tested. Therefore in small scale compounding polypropylene was melt mixed with hybrid fillers consisting of cellulose fibers and PCC in different ratios. The results further show, that even direct compounding of the `as produced´ slurry with polypropylene is a successful strategy for the preparation of a reinforced composite.