Mining modifies the surrounding environment and causes habitat deterioration along river systems receiving mine tailings. Here it is assessed whether chromium ore mining affects the odon. abundance and diversity. Line transect surveys were conducted during 4 months at the Henry river (along a pristine section and a previously mined section), and at the Lecing river, which is currently receiving tailings from chromium ore mines. The density of adult odon. was 10 times higher in the pristine than in the mined river. Species richness was reduced in both the currently and in the previously mined sections (5 spp.) as compared to that of the pristine river (12 spp.), showing a detrimental effect of chromium mining on dragonfly diversity and abundance.