CTradeoff, servizi e consulenza per Ie aziende, vicolo del Cedro 3B, 001 53-Roma (Italy) Abstract. Benchmarking is an approach used for evaluating and improving company performances, by comparing them to the best performing companies. Benchmarking first studies the process to be improved, evaluate the performances, finds a best practice process in order to try to match two parts of the processes which have analogies, and then tries to change or modify the interconnections, structures or behaviour of the part to be improved using the analogy with the best trasformation process, to transform performance evaluation into improvement decisions. In the paper, we try to define benchmarking from a modelling point of view, on the ground of a suitable representation of the production system.