In drilling engineering, well design usually starts with input of reservoir engineer. Based on requested hole size, hole length trough the reservoir, and other requirements, drilling engineer (well designer) can start its work. Afterwards, drilling engineer is collecting all available data from other engineers (geologists, petrophysicist, geomechanical engineers, etc) in order to design a well which will serve it purpose. In this thesis, geothermal well design approach will be discussed, with emphasis on geothermal well design in SE Europe. This thesis will try to find main oversights that are usually made in exploration phase. Also, it will be discussed how new findings during drilling of exploration well have changed the approach to design of further development wells.