Pests and plant pathogens are important reason of crops’ quality and productivity limitation. Che- mical drugs and pesticides belong to the most common among the strategies used to restrict losses in agricul- tural production. However, agrophags frequently acquire the resistance towards these substances, even after short time of contact with them. The occurring resistance is a natural consequence of the continuous evolutio- nary processes influenced by the selective pression of pesticides. The resistance results from point mutations and, in consequence, the changes of target protein’s structure for pesticides or the functional changes of other proteins, for example enzymes. The matter of the mechanisms of pesticides’ action and the formation of resistance is very extensive, therefore in this paper only chosen molecular mechanisms, that influence the oc- currence of resistance towards pesticides are discussed. Given examples had been restricted to the most com- mon pests and plant pathogens – insects, fungi, pathogenic bacteria, as well as herbs.