Possibility of selection of a particular reference picture from many previously encoded frames is one of the reasons of significant extension of time necessary for encoding of a video sequence with HEVC. Search of motion vectors within all available reference pictures for every PU (allowed by the HEVC standard) and selecting the best one, significantly enhances coding effectiveness but requires big computational effort leading to long encoding time. A fast method for selection of the best reference picture would be a source of shortening of the encoding time. This documents reports and verifies a method for fast reference picture selection in which reference picture list is pruned basing on the size of the PU under consideration. This way the number of reference picture necessary to look at the during motion vector search is reduced. Foundations of the reported method are the results of statistical analysis of the actual selected reference picture (considered by the encoder as the best in terms of RD) during encoding of the particular PU size.