Abstract. Weed infestation of faba bean grown in four four-course rotations, with a different proportion and position of this crop in the crop-rotation, was studied under conditions of mechanical and integrated (mechanical + undersown Brassica juncea ssp. juncea) weed control. Weed individual number and biomass provided a basis for calculating the indices of species diversity, evenness and domination. Relationships between the features of weed communities were also determined. The communities were compared based on coefficients of similarity. The integrated weed control was found to be equally effective as mechanical. Weed control methods had no effect on the examined features of weed communities (weed individual number, weed biomass, species diversity, evenness and domination), whereas the position of faba bean in the rotation affected weed abundance and biomass as well as modified the values of some biological indices. There was a strong positive correlation between the indices of species diversity, evenness and domination based on weed abundance and biomass. However, from the agricultural perspective, biomass-based indices seem to be more reliable. There-fore, it is recommended to conduct further studies involving multiple comparisons.