Calcium carbonate (CaCO3) is a natural occurring mineral or it can be produced by chemical means. This last product is often referred to as Precipitated Calcium Carbonate (PCC). PCC has various advantanges since it exhibits higher brightness and opacity. There can be considerable variation in the properties of the PCC depending upon the process conditions used to prepare it. In this work, the effect of different factors on the particle size of PCC has been investigated. The experiments were performed by bubbling CO2 in slaked lime suspensions. The pH of the lime slurry was 12 or higher at the beginning, but it decreased, down to an equilibrium pH of 8± 1, when the reaction was considered complete.