The impact of mature cow weight on the profitability of beef cattle farming and on the economic importance of the following traits was analyzed: calving performance, stillbirth and calf losses till weaning, birth and weaning weight, mature weight of cows, conception rates of heifers and cows and productive lifetime of cows. The cow weight was varied from 500 to 700 kg in 50 kg intervals. The economic efficiency of all farming systems was expressed as profit per cow and year. The program package ECOWEIGHT was used for all calculations. The results showed that beef cattle farming with all cow weight classes could be profitable when including subsidies in the incomes of a farm. Without subsidies, a positive profitability can be reached only when keeping small-framed cows (500 to 550 kg). In all modelled production systems, the most important trait was conception rate of cows followed by weaning weight for light cows or productive lifetime of cows in systems with heavy cows.