The multitude of medical laser systems with different wavelengths and technical appliances implicates the necessity of fundamental knowledge about the effects of laserbeams on living tissue. This is necessary to allow sufficient and therefore successful results for the patient. In this paper tissue effects of the mostly used lasers in otorhinolaryngology, CO2 laser and Nd:YAG laser will be presented. Influence on blood and lymphatic vessels, wound healing, and several CO2 laser parameters will be discussed.