The first thought conected with the term „weeds“ is that they are harmfull and unwanted plants. Weeds indeed can cause numerous damages, especially in agriculture where throughout competitive relations with cultivated plants they can significantly reduce the yield. Because of the need for additional works, weeds increase the cost of agricultural production. Except for agriculture, weeds can also cause damages in water management, health care, traffic, tourism etc. Also, each individual should be aware that weeds are not always harmfull, but can be useful. The aim of this final work was to present weeds as useful plants, or rather present the values and properties of individual species and their potential benefits to humans and the agroecosystem. In the agroecosystem weeds can improve the structure of the soil, prevent erosion, have a positive impact on other cultivated plants with allelochemicals, serve as mulch, be of use as compost or "green manure". A large number of weeds are edible and can serve as food for humans and animals. Numerous weeds are melliferous, medicinal or spices herbs so they represent bee pasture and sources of raw material for the food, pharmaceutical and cosmetic industries. Different weed species may be, due to their properties used for a variety of other uses – they can be used as natural dyes, for manufacture of mats, ropes, baskets, brooms etc.