During 6-week fattening period the growth of broiler rabbits of paternal line 59, maternal line 19 and their crossbreds was analysed. The crossbreeding effects (additive effect – AE, heterosis – HE and recombination loss – RL) were estimated for live weight (BW), average daily gain (ADG), average daily consumption (ADF) and feed conversion (FC). By the end of fattening period the crossbreds F1 were the heaviest ones (2802.5 g). For BW were AE of line 59 from 1.5 to 321,4 g during the whole fattening period.