Field studies were conducted in 2008–2010 at the Research Station Brody of Poznań University of Life Sciences. The aim of the study was to determine weed species composition and infestation in winter rye, oat and narrow-leaved lupin affected by the used tillage system (deep and shallow ploughing, reduced, direct drilling). The results of performed studies revaled the smallest number of weeds/m2 after the use direct drilling system, while the greatest values of weed fresh weight were related to the reduced tillage system. The dominant weed species according to weed density were Centaurea cyanus and Viola arvensis in winter rye canopy, especially in ploughless tillage. Chenopodium album and Polygonum convolvulus were the most numerous weeds in spring crops (oat, narrow-leaved lupin).