Due to its antimicrobial and antifungal properties, silver nanoparticles (AgNPs) are increasingly applied in consumer products as well as in various industries. However, because of their large surface area to volume ratio, AgNPs are highly reactive and subjected to silver ions (Ag+) release, which potentially increases their toxicity. So far, phyto-, cyto-and genotoxic effects of AgNPs to the various plant and animal organisms were observed. In this graduation thesis, the impact of 100 μM citrate-stabilized AgNPs and silver nitrate (AgNO3) on expression of total soluble proteins of tobacco (Nicotiana tabacum L.) seedlings and adult plants was examined. Two-dimensional gel electrophoresis was applied to analyse changes in protein profiles of whole tobacco seedlings as well as roots and leaves of adult plants, while mass spectrometry was used to identify proteins with different expression levels. It was revealed that AgNP and AgNO3 induced similar changes in the protein profiles of the certain tissue, while the expression level was found to be dependent on the developmental stage. Most of the proteins with altered expression are involved in the metabolism of carbohydrates, photosynthesis, response to stress and response to oxidative stress. The results showed that AgNP and AgNO3 mostly induced up-regulation of identified proteins in tobacco seedlings, while the protein expression was mainly reduced in the roots and leaves of adult plants. From the obtained results it can be concluded that the tobacco seedlings cope better with the stress induced with 100 μM AgNP and AgNO3 treatments compared to adult plants.