A rapid removal of Chernobyl ¹³⁷Cs from a number of large lakes has been previously reported. Our measurements of ¹³⁷Cs in water, sediments and pore water in the mono- and meromictic basins of Lake Lugano (Lago di Lugano) reveal generally slower half-removal times of 1.2 and 6.7 yrs, respectively. In the seasonally anoxic southern basin, this is most probably related to an intensive recycling of ¹³⁷Cs between water and sediments. In the permanently stratified northern basin the removal rate is much slower due to an important inventory build up in the deep anoxic part of the basin.