The research problem of the paper concerned verification whether applicable or known methods of post-harvesting evaluation of the roots of sugar beet may be applied to the assessment of the quality of work of technically varied new machinery for sugar beet harvesting. Tests of machines of varied solutions of working units, in particular a topping unit, were carried out in order to accomplish the objective of the paper. Two self-propelled combine harvesters of Ropa euro-Tiger V8-3 type and Kleine Beetliner Large and two sets for 2-stage harvesting by M.A.C.E (Spain) and Amity (USA) companies were used in the study. Ropa euro-Tiger and Kleine Beetliner Large combine harvesters and M.A.C.E. set were equipped with a beet topper but of a varied topping system, whereas, only a defoliator was used in the set by Amity company. Field research of machines included assessment of the topping quality, losses caused by the broken tip of roots and damages of the lateral surface of roots. Research assumptions were assumed according to the method of the International Institute for Beet Research (I.I.R.B.). Moreover, assessment of the topping quality with the method of the Netherlands Institute of Sugar Beet Research (IRS) and the Institute of Agricultural Engineering of the Bonn University was carried out. Assessment of roots after defoliation was carried out based on the Roller's classification (2010). Based on the research results and analyses which were carried out, it was proved that the methods of measurement of the quality of beet harvesting machines operation are not fully useful for assessment of the introduced technical and technological changes. It mainly concerns the assessment of the roots topping. Thus, two modified methods of assessment of the quality of roots topping were suggested. They may be used both for machines equipped with a topping device and a defoliator.