Blazars are relativistic jet dominated active galactic nuclei, whose emission in the optical region is mostly synchrotron in nature and therefore – polarized. We monitored several objects on intra-night time scales in order to study the changes in their linear polarization parameters in different colours. Our first results suggest the presence of rapid changes in both – polarization degree and the electric vector orientation even within a few hours. The intra-night polarization variability in many of these blazars is studied for the first time at such an extent. Our study can have significant impact on the detailed modelling of the relativistic jet emission mechanisms.