The reuse of process water in paper mills causes increase in the concentration of contaminants such as dissolved and colloidal substances (DCS) and electrolyte in the suspension. In this study, the effect of these materials on the retention or precipitated calcium carbonate (PCC) was investigated. The cationic microgels (CMG) with low charge density and cross-linked structure were compared to linear poly-DADMAC with higher charge density in the different model white water systems (WWS) including different concentrations of DCS and electrolyte. The results indicated that the main mechanism behind PCC retention for these two kinds of polyelectrolyte was patch-type electrostatic interaction in less and medium contaminated WWSs. On the other hand, a nonionic interaction was found in the highly contaminated WWS. It was also determined that PCC retention decreased with increasing contaminant concentration. CMG2 was less influenced by the contaminants because it had lower charge density and more stable and cross-linked structure as compared to CMG1 and poly-DADMAC. Additionally, SEM photos showed that PCC retention took place with bigger PCC flocks in the medium contaminated water. Yet, the flock size decreased with further increase of contaminant concentration.