Calcium carbonate precipitates are prepared from a solution of CaCl2 and K2CO3 in the presence of polyacrilic acid. The effect of polyacrilic acid incorporation in the [25-80 degrees C] temperature range on crystal morphologies and CaCO3 precipitated polymorph concentrations are investigated using scanning electron microscopy and X-ray diffraction quantitative microstructural and phase analysis. Large changes in morphology and phase proportions are observed in the presence of polyacrylic acid, which strongly depend on the solution temperature. While crystallization of vaterite is favoured in the presence of polyacrilic acid up to 50 degrees C, it is largely destabilized at higher temperatures. Our process also enables the elaboration of particles in the range 10-20 nm. (C) 2008 Elsevier B.V. All rights reserved.