Salts have a significant negative influence on mortars and plasters and consequently reduce their effectiveness. The diploma thesis describes the effects of salts on restoration plasters. For this purpose we prepared samples, made of loadbearing support and restoration plaster. In specially adapted chambers the samples were exposed to different environmental conditions (relative moistures and temperatures) and salts, in order to provoke accelerated crystallization and dissolution of salts. With the help of various laboratory techniques we analysed the damages on the samples that occurred due to the process of crystallization and/or dissolution of salts. We also describe the problems that we were facing during the experimental work.