Forest management practices usually preserves riparian buffers along watercourses in order to protect stream water from physical, chemical and ecological changes caused by clear-cutting. The purpose of this thesis was to investigate whether there is a relationship between the size of the riparian buffer zone along small streams, i.e., headwaters, and a number of physical and chemical attributes of these streams. Twelve headwaters in the Västerbotten county and twelve in Jönköpings county were investigated. These headwaters had a range of buffer widths from “No buffer” (no trees left), Thin buffer” (< 5 m wide), to “Moderate buffer” (>5 m wide) and “Reference” (no harvest) streams were also included. Tested physical and chemical conditions were light in the riparian zone, air and water temperature, stream bed cover and water chemistry. Buffer width had a significant effect on reducing light levels and temperature in the riparian zone; a buffer width over 13 m on each side of the stream was needed to maintain light and air temperature as in reference conditions. Regarding water temperature, increasing sedimentation and water quality, no significant reducing effect of increasing riparian buffer width was found.