The field experiment was conducted in the years 2014-2016 at AES Grabów (Mazowieckie Voivodeship), belonging to Institute of Soil Science and Plant Cultivation – State Research Institute in Puławy, (Poland) and in ecological farm in Chwałowice (Poland) in the years of 2014-2015. The trial was conducted in the randomized block method, in four replications. The following treatments were compared: control and intercrop sowings with: buckwheat, phacelia, white mustard and white clover. The inter-row cultivation of buckwheat, phacelia, white mustard and white clover had a positive effect on maize yield. On average, for the four species of the intercrops, the yield increase was 17-22%, and in Grabów, in the year with unfavorable distribution of total precipitation, this increase was significantly higher and amounted to about 60%. In the summers with favorable weather conditions (2014 and 2016), intersowing buckwheat proved the least useful in Grabów, while in the dry year, as well as in Chwałowice, this species was less competitive than maize. Intersowing different species into maize crops had a relatively small effect on the dry matter content of whole plants and cobs, while in Grabów in 2015, with unfavorable weather conditions, it had a positive effect on its content. In Grabów, the structure of maize plants was little diversified by the applied intercrop species. The lowest share of the cob was recorded in 2014. In Chwałowice, maize grown with intercrops formed cobs only in 2014. In this location, intercrops stimulated the number of grains produced per cob, while in Grabów, an intercrop species had a small impact on the number of grains per cob.