Construction or improvement of Serbian ski resorts produced numerous negative effects to surrounding environment, endangering even the functionality of the built objects. Investigation involved the analysis of disturbing activities by phases, and consequential environmental impacts. Clear cuttings, trunk transport, machine grading of slopes, huge excavations, and access road construction, caused the strongest pressure to the environment. Follow up activities during skiing and non skiing periods: skiing, usage of snow groomers, moving of vehicles and tourists, forestry activities and overgrazing. Consequential environmental impacts are clearly noticeable through intensive erosion processes, changes of hydrological conditions and forest fragmentation. The most affected ski runs were surveyed (scale 1:1000), all damages were mapped and classified during the summers of 2007-2010. Development of rills and gullies was measured at experimental plots (100x60 m), integrating survey data into GIS application. Changes of hydrological conditions were estimated on computations of maximal discharges before and after the construction of ski resorts, as well as using local hydrological records. Forest fragmentation is studied on the basis of detailed survey and field work.