When using the calculated energy content of harvested forage, it is possible to estimate also the future production of milk. This can be done by means of the programme MILK 2006 that was developed at the University of Wisconsin (USA). Using this system, results of three-year experiments performed with some chosen hybrids both in Troubsko and Prague-Uhříněves, were evaluated using the system MILK 2006. The estimation was based on the relationship between the potential milk production and the yield of dry matter (DM) per unit area. Estimated values of net energy per lactation were significantly correlated with estimates of milk production per ton of DM. Yields of DM ware significantly correlated with the potential milk production per hectare. However, these parameters were not the only factors that influenced final values. It is important to realise that from the economic point of view the final evaluation of maize hybrids represents a compilation of both criteria.