Our model simulations with the ozone-tagging technique show strong seasonal and daily variability in the contributions of various stratospheric and tropospheric sources to surface ozone over the Tibetan Plateau. Tropospheric sources from Central Asia, West Asian and Europe results in a summertime maximum over the northern Tibetan Plateau. The tropospheric source from South Asia and Southeast Asia leads to the peaks in the southern and central Tibetan Plateau during the pre-monsoon period.