The aim of the research was to assess the weed flora infestation in spring wheat cultivated in organic crop production system in comparison with conventional and integrated crop production systems. The study was conducted in 2005-2006 in the Experimental Station of the Institute of Soil Science and Plant Cultivation - State Research Institute in Osiny (Lublin province), where different crop production system are compared. The systems are characterised by different crop rotations and agricultural practices. In conventional and integrated system spring wheat was cultivated in pure stand, whereas in organic system it was grown with under crop (the grass with white clover and lucerne) as an element of weed regulation. In conventional system weeds were controlled by herbicides, whereas in integrated system the smaller amount of herbicides were used. Weed infestation was analysed qualitatively and quantitatively in the wax ripeness of spring wheat. Moreover the grain yield of spring wheat cultivated in compared crop production systems was assessed. Weed density was the largest in spring wheat cultivated in organic system (30-82 plants/m2), but their dry matter was low (5-13 g/m2) which suggests good competitive ability of wheat canopy with under crop. The number of weeds and weed dry matter was the smallest in conventional system (5-7 plants/m2, 2-3 g/m2). The grain yield of spring wheat differed in the years of research because of weather conditions, but it was the biggest in integrated system (3,2-4,2 t/ha). The effectiveness of weed control methods in spring wheat in three compared crop production systems was enough to maintain weed infestation on the level that not reduced the grain yield.