The effect of pour-point depressants (PPD) of the polyalkylacrylate-type on n-paraffin solutions (C-20-C-36) has been investigated with the help of pour-point measurements (Knauer automatic MC850). Dependent on the chain length of the n-paraffins several maxima in pour-point depression efficiency were found. The locations of these maxima are strongly influenced by the molecular weight and m.w. distribution of the polymeres used as PPD. The solubility of the polymers in the solvent of paraffin solutions is another important factor determing the location of the optimal efficiency. These factors (solubility, molecular weight and m.w.-distribution of the polymers) could be important for the efficiency of the PPD in paraffinic crude oils as well. For crude oils the concentrations and distributions of the higher n-paraffins are additional parameters affecting the behaviour of the PPD. The optimum effect of the PPD for crude oils is to be expected for largely overlapping cristallisation temperature-ranges of the polymers and the n-paraffins.